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HUMAN PHYSIOLOGY 


DESIGNED FOR 


COLLEGES AND THE HIGHER CLASSES IN SCHOOLS, 


AMD 


FOR GENERAL READING. 


BY WORTHINGTON HOOKER, M. D, 

PROFESSOR OF THE THEORY AND PRACTICE OF MEDICINE IN VALE COLLEGE; 
AUTHOR OF “ PHYSICIAN AND PATIENT.” 


Illustrated by nearly 200 Engravings. 


NEW YORK: 


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Entered according to Act of Congress, in the year 1854, by 
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CONTENTS 


PART I. 

CHAPTER I. Pa3 „. 

Organized and Unorganized Substances. . . .13 

CHAPTER II. 

The Distinction between Animals and Plants. . 2' 

CHAPTER III. 

Man in his Relations to the Three Kingdoms of Na¬ 
ture, . 27 

PART II. 

CHAPTER IV. 

General Views of Physiology, with a Brief Account 

of some of the Structures of the Body, . 35 

CHAPTER V. 

Digestion, .42 

CHAPTER VI. 

Circulation of the Blood,.64 

CHAPTER VII. 

Respiration,.86 

CHAPTER VIII. 

Formation and R,epair, ...... 109 

CHAPTER IX. 

Cell Life,. 123 







IV 


CONTENTS. 


PART III. 


CHAPTER X. 

The Nervous System,. 

Page 

139 

The Bones, . 

CHAPTER XL 

170 

The Muscles, . 

CHAPTER XII. 

196 

The Language of 

CHAPTER XIII. 

the Muscles, .... 

222 

The Voice, 

CHAPTER XIV. 

243 

The Ear, 

CHAPTER XV. 

271 

The Eye, 

CHAPTER XVI. 

287 

CHAPTER XVII. 

Connection of the Mind with the Body, 

# 

318 

CHAPTER XVIII. 

Differences between Man and the Inferior Animals, 

347 

Varieties of the 

CHAPTER XIX. 

Human Race,. 

367 

Life and Death, 

CHAPTER XX. 

381 

Hygiene, 

CHAPTER XXI. 

390 

APPENDIX, . 

. 

411 







PREFACE. 


I have aimed so to write this book, that it shall be fitted both for gen¬ 
eral reading, and for instruction. It is designed for the family as well as 
for the school. It seemed desirable that these two objects should be ae 
complished at the same time, and I have not found them to be at all in¬ 
compatible. The instruction needed by the family on this subject, differs 
not from that which is required in the school-room, either in regard to 
the facts to be communicated, or the manner in which it should be done. 
No one will question the truth of this, so far as the facts are concerned. 
But it is true even as to the mode of communicating them. In both cases 
there need to be clearness in statement, and fullness of illustration. Actual 
instruction is to be given in both cases, and to minds that are very nearly 
in the same attitude. I could not, therefore, see the necessity of writing a 
book on this subject for the people which should differ from one written 
for the school. Besides, it has seemed to me desirable that there should 
be a greater community of interest between the school and the family than 
as yet exists; and this object books equally interesting to both will tend 
to promote. 

It may be proper for me to say a word in relation to the style of the 
work. I have adopted the style of the lecture-room, because, that while 
it is not inconsistent with conciseness, it is the more natural mode of in¬ 
struction, especially when so much reference is made to illustrative figures. 
It has enabled me also to keep in view more effectually the attitude of the 
minds I address. I have had my readers before me continually as an 
imaginary audience. I have avoided technical terms as far as possible. 
Whenever they are used they are sufficiently explained at the time, so 
that no glossary is needed. Some points commonly considered hard to 

be understood are treated of, but I have endeavored to simplify them, bv 

1 * 



VI 


PREFACE. 


full illustration, and by a presentation of the truth uncomplicated with 
speculations and hypotheses. And these points are so introduced, that 
the mind is prepared by the previous investigation to understand them. 
I have aimed so to arrange the topics, as to have a preparation constantly 
going on in the mind of the student, fitting him for the proper under¬ 
standing of what is to come after. By this natural gradation in the de¬ 
velopment of the whole subject some of the deep things in Physiology 
can be made clear, which it would otherwise be impossible for the student 
to understand. It is proper to state here, that I intend to prepare a worK 
for younger scholars, in which some of the simple points in Physiology 
will be illustrated. This, by familiarizing their minds with the subject, 
will fit them for a more thorough understanding of the present work. 

Although Physiology is becoming a prominent study in the schools and 
colleges in some parts of our country, its importance is no where as yet 
appreciated as it should be. It should be made a regular branch in our 
Educational System. This has been already done in France. “ A com¬ 
petent knowledge,” says Carpenter, “ of Animal Physiology and Zoology 
is there required from every candidate for University honors; and men 
of the highest scientific reputation do not think it beneath them to write 
elementary books, for the instruction of the beginner.” 

The importance of Physiology as a study, will appear from various con- 
siderations. 

Many of the subjects comprised in Physiology have, in the case of 
most students, been already studied in a different phase, or mode, in other 
branches. Thus, if the student has attended to the Mechanical Powers 
m his Natural Philosophy, he finds in the human body the principles of 
the pulley and the lever illustrated in great variety and perfection. The 
principles in relation to strength in the form and arrangement of struc¬ 
ture he sees exemplified in the frame-work of the body in the most ad¬ 
mirable manner. If he has studied Hydraulics, he sees in the body the 
most perfect, and at the same time the most complicated hydraulic ma¬ 
chinery, working incessantly throughout life in the circulation of the 
blood. The principles of Pneumatics he finds applied in the respiration— 
those of Optics in the eye—those of Acoustics in the ear—and those of 
Musical Sounds in the apparatus of the voice. And then, his chemical 



PREFACE. 


Y1I 


knowledge meets with new applications in his observation of the changes 
and the processes going on in the body. 

The relations, then, of Physiology to some of the common branches 
taught in the higher classes in schools, are of the most intimate charac¬ 
ter. Physiology, in part, merely extends these branches into a new and 
interesting field ; and the student who has once entered this field recurs 
to these same branches with a renewed interest. Hydraulics, Pneuma¬ 
tics, Optics, &c., have now a new attraction for him, from this, to him 
novel, application of their principles. The interest thus awakened in 
his mind is worth much in itself, aside from the mere addition made to 
his knowledge. And the interest is enhanced by the consideration, that 
in the human body he sees the applications of these principles to mechan¬ 
ism that exhibits the skill of perfect wisdom and almighty power. 

But there are relations of Physiology to still other studies which should 
be noticed. 

The analogies that exist between the human body and all other living 
things, in relation to structure and growth, are numerous and striking. 
Thougli life is so diverse in its processes and in the forms which we see 
it evolve in the whole range of animated nature, it in some important re¬ 
spects displays a great similarity, which it is interesting to trace through¬ 
out its diversified manifestations. Growth, or nutrition, as you will see 
in the following pages, is essentially the same in the Plant as it is in the 
Animal. Botany, therefore, taught as it should be, has quite an intimate 
relation to Animal Physiology. The Science of Life is, in many respects, 
one Science; and if, in studying any of its subdivisions, we fail to take 
this broad view of it, and to trace out the analogies referred to, we lose a 
large part of the interest of the study. Human Physiology, the subject 
of study in this book, is but a part of a science which offers to the student 
wide fields of observation exceedingly diversified and full of interest. 
This being so, I could not avoid in the following pages making occasional 
reference to the analogies existing between the phenomena of life as ex¬ 
hibited in the human system, and those which we see in the living world 
around us. So that as the student proceeds with the study, he will find 
himself interested in the phenomena of life in whatever form they are 
presented. 



Vlll 


PREFACE. 


Tliis leads me to say that this study of nature, in its broad common re¬ 
lations and its beautiful and extensive analogies, should be made very 
prominent in our systems of education. It is the application of the prin¬ 
ciples of abstract science to the forms, and especially the living forms of 
nature all about us, that gives interest to these principles, and makes us 
to understand and appreciate them. It is here that we find a very seri¬ 
ous defect in the prevalent mode of education, even at the present time, 
notwithstanding all our improvements. Let us look at it a moment. We 
live in the midst of a material world, animate and inanimate, and have 
daily converse, so to speak, with material forms of every variety, present¬ 
ing phenomena of the highest interest and of endless diversity. And 
yet, through almost all the period of childhood, and perhaps we may say 
youth also, this book of nature is in the school-room very nearly a sealed 
book. The very process of education shuts in the pupil from this broad 
contemplation of the world in which he lives. He is drilled through 
spelling, reading, grammar, &c., but he is left in total ignorance of the 
beautiful flowers, and the majestic trees outside of the school-room. How 
very few even of thoroughly educated adults, know the processes by 
which a plant or a tree grows! And the same can be said of other 
phenomena of nature. 

The defect which I have pointed out runs through the whole of educa¬ 
tion. We can see it even in the prevalent mode of teaching the natural 
sciences themselves. One would suppose that here the facts, the phe¬ 
nomena, would command the chief attention of the teacher and the stu¬ 
dent. But it is very commonly not so. The mere technicalities and the 
classification are made much too prominent. . Botany, really one of the 
most interesting of all branches of natural science, is thus ordinarily 
made one of the driest of studies. To teach this aright, the phenomena 
of vegetation, so varied and so beautiful, should constitute the chief ma¬ 
terial of instruction, and the mere classification should be considered, al¬ 
though necessary, as wholly a secondary thing. 

The great facts of the world, both of mind and matter, should furnish 
really the material for education, and those branches that are ordinarily 
pursued with such assiduity should be considered as merely subsidiary to 
the teaching of these facts. The whole order of education must be re- 



PREFACE. 


PS 


versed. Instead of beginning the child’s education with learning to spell 
and read, the object should be to make him an observer of nature, and 
the spelling and reading should be done in connection with this, and as 
subsidiary to it. Things and not words, or mere signs, should from the 
first, constitute the substantial part of instruction. The child should be 
made, at home, in the school, and everywhere, a naturalist in the largest 
sense of that word. We should aim to impart to him a spirit in con¬ 
sonance with the following precept of Hugh Miller, the famous self- 
taught geologist. “ Learn to make a right use of your eyes; the com¬ 
monest things are worth looking at—even stones and weeds, and the 
most familiar animals.” 

As it is now, no one becomes a naturalist early in life, except in spite 
of the tendencies of his education. The study of nature is not only not 
encouraged, but is absolutely discouraged in our educational system. If 
any one, like Hugh Miller, by the force of a taste that can not be repress¬ 
ed by the training of the school-room, undertakes to make a “ right use 
of his eyes,” and curiously examines “ stones and weeds,” he is regard¬ 
ed by the world of spellers and readers and grammarians and cipherers, 
as a strange genius. But he is pursuing from an irresistible internal 
force, the very course that I would have every student, even from his 
childhood, encouraged to pursue, in a measure at least, by the external 
circumstances of his education. The tendencies of his training should be 
decidedly in this direction. 

If the general mode of education were changed in the manner indicated, 
education would have much less of the character of mere drudgery than 
it now has. Not that there would be any the less labor: but the labor 
would be made lighter by the interest imparted to it—the interest, which 
always results from the study of facts and phenomena, and never from the 
learning of mere words and technicalities and classifications. I would 
gladly dwell on this subject, and show by varied illustrations how the 
mode of instruction referred to, should be pursued, and especially with 
younger scholars 5 but the limits of a prefaoe will not allow me to enter 
so large a field. 

The change which I have pointed out can not be effected at once. It 
will require time. Confirmed traditional customs are to be done away, 



X 


PREFACE. 


the habits of teachers are to be altered, and the proper books are to 4 
great extent to be yet written, especially such as are fitted for the first 
years of education. 

If the study of nature should be thus made prominent in education, 
human physiology would be considered altogether its most interesting and 
important branch, and for several reasons. First: there is no where to 
be found so curious a collection of mechanisms, or so interesting and 
wonderful a series of processes, as in the human body. In nothing else 
in the wide world are the principles of so many departments of science 
so extensively and perfectly exemplified. Life works here its most com¬ 
plicated set of machinery. Secondly: the singular and mysterious con¬ 
nection of the immaterial and immortal soul with the material and perish¬ 
able body, gives intense interest to this study. In Physiology we do 
not study matter alone, or spirit alone, but both matter and spirit united, 
and often acting together. This circumstance distinguishes this from all 
other studies. Thirdly: it is our own frames, moved by the spirit within 
us, that we study. The subject has a personal interest for us, that is not 
presented by most studies, and by none in so large a degree as in this. 
And Fourthly: the study is of great importance, because a judicious and 
efficient Hygiene must be based upon a knowledge of the laws of physi¬ 
ology. We cannot know how to keep our functions in the condition of 
health, without understanding the laws that regulate them. I have said 
but little in this book in regard to hygiene, and that only incidentally, be¬ 
cause that subject would require of itself a whole volume to elucidate it 
properly. 

I have not thought it proper to indulge to any great extent in those re¬ 
flections, which the contemplation of so perfect and diversified a congeries 
of mechanisms as are presented in man would naturally suggest, in regard 
to the skill of the great builder of the universe. Such reflections would 
extend the book to too great length. Besides, they are so readily sug¬ 
gested to the mind of both teacher and scholar, that it is entirely un¬ 
necessary for the author to dwell on them. 

I have treated of some subjects, on which, from the difficulty of un¬ 
derstanding them, there has been a disposition in many minds to go be¬ 
yond what we know, and indulge in unwarranted speculation. On these 



PREFACE. 


XI 

points I have taken pains to draw the line very distinctly between what is 
known, and what is supposed. I deem it to be important to prevent the 
minds of the young from being led away from the simple truths of 
science by ingenious speculations and plausible reasonings. Let me not 
be understood to decry all hypothesis. I only object to the mingling of 
facts and suppositions together in one indiscriminate mass, as is often 
done. The disposition to do this, which is more common than is generally 
supposed, exerts so injurious an influence upon the habits of the mind, 
and so confuses its views of truth, that we ought to look upon it as one of 
the most serious evils to be guarded against in education. It is really 
one of the most prominent obstacles to the progress of truth on all sub¬ 
jects, both in individual minds, and in the minds of the community at 
large. This disposition, so apt to be fostered in the enthusiastic mind of 
youth, by ingenious but dreamy speculations, should be corrected at the 
outset, and the mind should in its forming stage, be habituated to the dis¬ 
crimination between the proved, the true, and that which rests on pre¬ 
sumptive, perhaps merely plausible evidence. This discrimination should 
therefore be exemplified in books designed for instruction, and this I have 
attempted in the present volume. 

I have divided the book into Three Parts. The First, which I have 
made as short as possible, is merely preliminary to the consideration of 
the particular subject of the book. In the Second Part, I present the 
human structure, simply as a structure , and show how it is constructed 
and kept in repair. In the Third Part, I treat of all those subjects which 
relate to the uses for which the structure is designed. This natural 
division of the whole subject, not only presents it to the mind of the 
student in an interesting point of view, but secures that natural grada¬ 
tion in its development, which I have spoken of as being necessary to a 
dear understanding of its deeper and more intricate portions. 



NOTE. 


Since the book was first published, the Author 
has, in obedience to the requests of many Teachers, 
added a chapter on Hygiene, and also an Appendix 
containing questions. A .full Index is also subjoined. 



PHYSIOLOGY 


PART FIRST, 

CONTAINING, 

CHAPTER I —Organized and Unorganized Substances. CHAPTER II.— The Distinction 
between Animals and Plants. CHAPTER III.— Man in his Relations to the Three 
Kingdoms of Nature. 


CHAPTER I. 

ORGANIZED AND UNORGANIZED SUBSTANCES. 

1. The crystal and the plant are both wonderful growths . 
As you look at them, you think of the crystal as having been 
formed, and of the plant as having grown. But in one sense 
they have both grown to be what they are. The crystal was 
once a minute nucleus, and the plant was once a little germ. 

2. In one respect they are alike in their growth—both have 
increased from particles taken from things around them. But 
the processes by which this is done are different in the two 
cases. The crystal has increased or grown by layer after layer 
of particles. There are no spaces or passages by which parti¬ 
cles of matter can be introduced inside of it. Any part of it, 
when once formed, is not altered. It can receive additions 
upon the outside alone. But it is not so with the plant. This 
enlarges by particles which are introduced into passages and 
interstices. It grows, as it is expressed, by absorption or by in ¬ 
tussusception . 

3. How, now, is this absorption effected? It is done hv cer¬ 
tain vessels or organs , constructed in the root of the plant for 
this purpose. These take up or absorb fluid matter from the 
earth. There are other organs which circulate this fluid through 
all the plant; and others still which use it for the purpose of 
growth or formation. There are no such organs in the crystal, 
for it has no inner ’growth. The plant is therefore said to be 
an organized substance or being, and the crystal is an unor ¬ 
ganized substance. And so we speak of the organic structure, 
or the organization of plants. 


2 




14 


HUMAN PHYSIOLOGY. 


Organized beings. Mechanical, chemical, and vital principles. 

4. These organs, which thus absorb, and circulate, and con¬ 
struct, do not act simply on mechanical principles. The plant 
is not merely soaked with fluid, which the heat of the sun may 
expel, as it does water from a porous mineral substance. These 
organs are active agents, and they perform their duty with a 
force, and after a manner, for which no mechanical principles 
can account. No mechanical powers could alone supply the 
leaves of the mighty tree of the forest with sap from its deep 
roots; much less could they form these leaves. 

5. Neither do these organs act simply on chemical princi¬ 
ples. While man, through the agency of chemistry, can form 
some of the crystals which are found in nature, he can not by 
any arrangement of constituents make a plant, a flower, or a 
leaf. And the plant, left alone to the action of chemical prin¬ 
ciples, wilts; and at length ceases to be a plant, and becomes 
common unorganized matter. 

6. Mechanical and chemical principles, it is true, are both 
employed to some extent in the growth of plants; but they are 
under the control of other principles, which we term vital. And 
so we speak of the plant not only as an organized substance , 
but as a living being . 

7. What I have said of plants, in distinction from minerals, 
may also be said of animals. They are also organized living 
beings, and they have generally a more complex organization 
than plants, as you will see as I proceed. 

8. The whole material world, then, that we see around us, 
we divide into two parts—the unorganized and lifeless, and the 
organized and living. The distinctions thus pointed out be¬ 
tween organized and unorganized matter are essential and 
fundamental. But let us look at some other distinctions, which 
either arise from these or accompany them. 

9. One distinction is this. All the parts of the mineral are 
independent of each other, while it is otherwise with the plant 
or the animal. Accordingly, we examine the properties of min¬ 
erals in a different way from those of plants and animals. The 
chemist can ascertain all the properties of a crystal or a rock, 
if you give him but a small piece of it. But the botanist can 
not ascertain all the properties of a plant by looking at some 
one part of it. If he examine the flower, this gives him no 
knowledge of the root. In order to know all about the plant, 
he must examine every part by itself, and then look at it in its 
relations to the other parts. The same can be said of the 
physiologist, in his investigation of the properties of animals. 





ORGANIZED AND UNORGANIZED SUBSTANCES. 15 


Assimilation in organized substances. 

.10. As the crystal is forming by layer after layer of particles, 
no change is effected in these particles as they are becoming 
arranged in the layers. But in the case of the living organ¬ 
ized being, a change is produced in the particles which are 
taken up by the absorbents. And the change, ordinarily, is 
both a gradual and a complex one. In the plant, a change is 
produced in the particles in the very act of absorption; but 
this change is only the beginning of a process which is after¬ 
wards perfected. The sap is not thoroughly fitted for nutrition 
when it first begins to circulate. It is carried up through the 
vessels of the trunk or stalk to the leaves. There the last step 
of the process is taken, and the sap is now ready to be used in 
the growth of the plant or tree. So, also, in the animal, the 
nutritious part of the food, taken up by the absorbents in the 
digestive organs, is first acted upon by certain little glands, 
through which it passes, is then poured into the circulation, to 
be mingled with the blood, and is carried with the blood to the 
lungs, to be exposed to the air; and thus it is fitted for the nu¬ 
trition' or growth of the body. This process, which is thus car¬ 
ried on in the plant and in the animal, is very properly called 
assimilation. For the particles that are taken up by the ab¬ 
sorbents in the root of the plant are, by this process, made like 
to the plant; and the particles taken up by the absorbents in 
the stomach * are made like to the animal. So obvious is this, 
in the case of the animal, that some French physiologist speaks 
of the blood as chair coulante , or running flesh. 

11. Another prominent distinction between organized and 
unorganized substances is in relation to 'permanency. Constant 
change appears in all organized bodies; while permanency is 
written upon all substances which are unorganized. In organ¬ 
ized beings, continual change is going on at every point. It is 
a condition of their being. This is true, not only of the de¬ 
cline of a plant or animal, but even of its growth. For, in its 
growth, as the parts enlarge internally as well as externally, 
they change not only the arrangement of the particles, but, to 
a great extent, they change the particles themselves. It is 

* The word stomach requires some little explanation, as it is used in physiology in two 
senses—in a limited sense, and also in an extended one. It is used in its limited sense, as 
referring to the cavity at the beginning of the alimentary canal , as it is termed; this lat¬ 
ter term being applied to the series of cavities, the stomach and the small and large intes¬ 
tines, which are found in the digestive apparatus in the higher orders of animals. In 
comparisons, however, between these animals and those which have a more simple digest¬ 
ive apparatus, the word stomach is used in a more extended sense, as being synonymous 
with the term alimentary canal. It is used in this sense, also, when, as in the present 
ease, it is referred to in a comparison between animals and vegetables. 








16 


HUMAN PHYSIOLOGY. 


Organized substances changing. Unorganized permanent. 

true, as well of the towering tree as of the tiny plant, that 
these changes have been going on during all its growth; so 
that, at its maturity, it is, both in relation to the arrangement 
of its particles, and in relation to the particles themselves, a 
very different thing from what it was when it pushed its germ 
up through the ground, or even when it was but a small tree. 
Not only has it received into its interstices and passages new 
particles, but it has thrown off from the pores of its leaves, 
those outlets for the refuse of plants, vast quantities of parti¬ 
cles which are no longer of use in its structure. So, in all 
animals, the same internal changes are going on, and to a 
much greater extent; because, from the activity of their na¬ 
ture, there is more of wear and tear, and, therefore, more of 
refuse matter to be disposed of. As you will see in another 
part of this book, the human body, that most complicated of 
organized beings, undergoes these changes very largely. 

12. It is not thus with unorganized substances. The crys¬ 
tal, so fast as it is formed, becomes permanent. No changes 
occur within it. In itself, it is unchangeable. It can not 
change its own particles, as the plant or the animal does. It 
can be changed only by external addition, or by external dimi¬ 
nution, through the influence of agents acting upon its surface. 

13. With the constant changes going on in organic nature, 
there is constant succession. Plants and animals produce other 
plants and animals, and themselves die, making room for their 
successors. But the crystal does not form other crystals, and 
then crumble into dust. In itself, it is both unchangeable and 
unproductive. 

14. This distinction between organized and unorganized sub¬ 
stances, in relation to change and succession, meets the eye 
everywhere. The mountains, the rocks, and even the stones 
under our feet, remain the same year after year, while all vege¬ 
table and animal life is ever changing its forms and manifesta¬ 
tions. There are the changes of growth, and the changes of 
decay and death, all around and within us; and they are 
strangely mingled together. There is death even in the 
changes of life, as the waste particles are taken away, and are 
replaced by the new; and life springs out of the very bosom 
of death, as from decayed nature new forms of vigor and 
beauty arise. The mountains stand as they have stood, as the 
passing generations have looked upon them, while the continual 
changes of vegetation have been going on upon and around 
them. The seasons crown their battlements with the emblems 





ORGANIZE!) AND UNORGANIZED SUBSTANCES. 17 

Different forms of organized and unorganized substances. 


of their ever-returning mutations of life, decay, and death; 
and even the mighty trees, that have shed their leaves from 
year to year, in obedience to the great law of change, but have 
themselves stood, at length bow their heads to the same law, 
and give place to other lords of the forest. From the “ ever¬ 
lasting hills,” which thus remain the same, though change is 
ever about and upon them, man gets the unchangeable and 
imperishable rock to construct liis habitation, while he himself 
is changeable and perishable—the creature of a day, whose 
life is as a vapor. lie wears the precious stones, and traffics 
in the golden ores, which have existed from the creation of the 
world, through all the changing and dying generations, and 
passes away, leaving them to others as changeable and perish¬ 
able as himself. 

15. Another distinction between organized and unorganized 
substances relates to the forms which they assume. There is 
regularity in both, but it is different in each. Unorganized 
matter is disposed to arrange its particles in straight lines, and 
with angles mathematically exact. You see this in the beautiful 
crystal; and you also see it, less definitely, but magnificently, 
displayed in the regular battlements and columns of rocks and 
mountains. The tendency is to regularity; and irregularity is 
the result of interfering circumstances. A similar disposition 
to regularity is manifest in organized substances, but in a 
different manner. It is disposed to curved, rather than straight 
lines, and seldom makes lines or angles with mathematical ex¬ 
actness. We see this law of regularity exemplified both in 
animal and vegetable life. The leaf, for example, has the same 
general shape, that is, the same general arrangement of par¬ 
ticles, when it attains its full size, that it had when it was 
small; and the same can be said of the arm of the man, com¬ 
pared with his arm when a child. Illustrations might be cited 
to any extent, but these are sufficient. 

16. While the law of regularity is not commonly as exact 
in organized substances as it is in the unorganized, it is quite 
as authoritative. While it does not ordinarily observe the per¬ 
fectly straight lines and the unvarying angles which we always 
find in the crystal, the general plan and contour are very strictly 
preserved amid all the changes of animal and vegetable life. 
And, in some cases, the same mathematical exactness that we 
find in the mineral world is found in organized beings. I 
know not that this is ever true of straight lines and angles; 
but it is often true of curved lines. There are many very 





18 


HUMAN PHYSIOLOGY 


Regularity in form—in some cases wonderfu/- 

beautiful examples in the vegetable world. I will give but a 
single one. If you look at the common white daisy, before the 
hundreds of little buds in its bosom have opened into tiny 
flowers, you will see them arranged with great exactness in 
crossing curved lines, such as you often see on the back of 
a watch case. A similar arrangement you will find in many 
flowers. 

17. This regularity is more wonderful in organized sub¬ 
stances than in the unorganized, because it rules in them in the 
midst of constant change. In the case of the crystal, as there 
are no internal changes in it, and as each layer of it, when 
formed, is permanent, regularity is comparatively, so to speak, 
easily secured. But in the case of the leaf, as it is growing to 
its full size, and of the arm, as it grows from infancy to bo 
the stalwart arm of manhood, continual change is going on at 
every point; and regularity here is obviously a more difficult 
achievement. 

18. This regularity appears still more wonderful, when we 
look at the infinite variety of forms in organized matter, in 
both the vegetable and the animal world. In all these forms, 
each part of every animal and of every plant maintains its 
own peculiar plan and contour. Take, for example, the leaf in 
its endless varieties. IIow definitely does each variety preserve 
its individual character, and how easily is it distinguished from 
every other variety! The same can be said of every part of 
every organized being. 

19. Another circumstance still must be mentioned, as adding 
to the wonderfulness of this regularity. It has been scrupu¬ 
lously maintained, through all the changes of the world from 
its creation, when God pronounced the works of his hands to 
be “ very good.” The leaf of every tree, for example, is like 
the leaf of its ancestral trees back to that time; and so it will 
be in all its successors to the end of the world. “The trees of 
the garden,” which delighted the eyes of our first parents, and 
refreshed them with their shade in their innocence, and amid 
which they hid themselves after their sin from the presence of 
their Maker, undoubtedly had the same characteristic shapes, 
and the same leaves and flowers which their successors present 
to our eyes. 

20. Again, it is interesting to notice that, in the midst of 
this regularity, so strictly maintained in each specific form from 
age to age, there is a measure of irregularity allowed. While 
each kind of tree, for example, has specific characteristics in 







ORGANIZED AND UNORGANIZED SUBSTANCES. 19 


Variety of form; yet regularity preserved. Size. 

the arrangements of branches and other parts, and in the 
shapes of its leaves, no two trees of the same kind are exactly 
alike, and there is always much variety in the leaves of the 
same kind. The wonder is, that so much latitude is allowed 
in this respect, and yet the specific characteristics of each kind 
are so thoroughly preserved. We can readily see that if a 
pattern, definite in all its details, were to be copied exactly in 
each kind of vegetable and animal form, the distinctions between 
them could be more easily preserved. But Omnipotence is 
able to combine a wide latitude and variety of form in each 
kind, with a strict and uniform preservation of its characteristic 
contour and arrangement. We have a striking exemplification 
of the above remarks in the variety of the human countenance. 
While the face of man is so entirely different from the face of 
every other animal, at the same time, among the hundreds of 
millions of the human family, how uncommon it is to find two 
faces that are very nearly alike. 

21. In the animal world, we see remarkable examples of the 
preservation of regularity of form in the exact correspondence 
which exists so commonly between the two halves of the body. 
For example, the brain has two halves, which are precisely alike, 
and the same is true of the nerves which are distributed from 
it. And so of other parts. But, mingled with this symmetri¬ 
cal arrangement of parts, there are other parts which are irreg¬ 
ular in their shape. This is the case with the stomach, the 
heart, the liver, &c. There are some animals which are alto¬ 
gether destitute of this arrangement of two similar halves of 
the body. The oyster is a familiar example. The shell of this 
animal is strikingly in contrast, in this respect, with the shells 
of some other of the bivalve tribe, as, for instance, the common 
clam. 

22. There is a distinction between organized and unorganized 
substances, in regard to size , which must not pass unnoticed in 
this connection. The size of unorganized bodies has no fixed 
limit. A crystal or a rock may grow to any imaginable size, 
if the particles forming it are sufficiently abundant. But or¬ 
ganized bodies have limits fixed to their growth. There is, it 
is true, more or less latitude to these limits; but they are so 
well defined in the case of most vegetables and animals, that 
when growth reaches much beyond or below the limit, it is 
recognized as a remarkable fact. Gigantic and dwarfish vari- 
ties are rare exceptions to the general rule. 

23. The last distinction, between organized and unorganized 






20 


HUMAN PHYSIOLOGY. 


Difference between organized and unorganized in structure and elements. 

substances, which I shall mention relates to their structure. 
While unorganized substances are made of one form of matter, 
either solid or liquid, or gaseous, organized bodies are made of 
a mixture of fluids and solids. They are therefore more or less 
soft and flexible; while the solid, unorganized substances are 
hard and brittle. There is a still further difference in struc¬ 
ture. Organized substances are much more compound than 
the unorganized. Most of the unorganized substances are 
composed of only two or three elements. Thus, air is com¬ 
posed of oxygen and nitrogen, water of oxygen and hydro¬ 
gen; and most of the mineral salts are composed of three 
elements—as, for example, carbonate of lime, or chalk, which 
is composed of oxygen, carbon, and calcium, the mineral base 
of lime. But organized substances are composed of at least 
three or four elements, and sometimes more. The four princi¬ 
pal elements in the composition of organized bodies are, oxygen, 
nitrogen, hydrogen, and carbon. But there are other elements 
introduced for special purposes. Thus, carbonate of lime (a 
combination of calcium with two of the common elements, 
carbon and oxygen,) is diffused very generally throughout the 
textures of plants, giving them firmness and strength. In the 
grass tribe, silex is deposited under the surface, producing the 
necessary combination of strength and lightness, a very small 
quantity of the silex answering the purpose. In animals of 
the higher orders, phosphate and carbonate of lime compose in 
part the framework of the body. We find iron, too, in the 
blood. Of the fifty-four elementary substances discovered in 
mineral bodies, only eighteen or nineteen have been found in 
plants and animals, and some of these in very small amounts. 
The essential components of living substances are the four non- 
metallic elements mentioned above—oxygen, hydrogen, nitro¬ 
gen, and carbon; while the bulk of the inorganic world is 
composed of the metals and their compounds, viz., the alkalies 
and the earths. And it is interesting to observe that, of the 
four elements which compose the bulk of the animal and vege¬ 
table world, both the fluids and the solids, three are gaseous, 
while but one, carbon, is a solid substance. 





DISTINCTIONS BETWEEN ANIMALS AND PLANTS. 21 


Locomotion. Stomach and other central organs. 


CHAPTER II. 

THE DISTINCTIONS BETWEEN ANIMALS- AND PLANTS. 

24. Having pointed out in tlie first chapter the distinctions 
between organized and unorganized substances, I now proceed 
to consider the distinctions between the two classes of organ¬ 
ized beings—animals and vegetables. I shall first notice those 
differences which are obvious when we look at the great major¬ 
ity of animals and vegetables; and shall then point out those 
which are essential , in order that we may have a clearer view of 
those exceptional cases, in regard to which it is somewhat 
difficult to decide to which of the two kingdoms they belong. 

25. One of the most obvious distinctions is in relation to 
locomotion. The plant remains in one place; while the animal 
moves about, in the air, or in the water, or upon the surface of 
the earth. And the structures of the animal and the plant of 
course differ, so as to accommodate these two very different 
modes of existence. I will particularize. As the animal moves 
from place to place, it must, for this reason, if for no other, 
have an apparatus of nourishment and growth different from 
that of the plant. The plant, by means of its absorbents in 
the roots, takes up from the earth, in the form of sap, its nutri¬ 
tion, or food, as it may very properly be called. The moving 
about of the animal would in itself forbid its deriving its food 
directly from the earth, even if the earth contained the proper 
materials for its nourishment. Another contrivance must 
therefore be resorted to, in order to effect nutrition in its case. 
So a cavity is provided in its body, called a stomach, into 
which nutritious substances can be introduced. And this cav¬ 
ity is lined with absorbents, which there do for the animal 
just what the absorbents in the roots of the plant do for the 
plant. 

26. Besides the stomach, there are other great central or¬ 
gans which are peculiar to most animals, in distinction from 
vegetables—as the heart, the liver, the lungs, &c. In the 
plant, there are no such central organs upon which the whole 
plant depends. Branches and roots may be cut off extensively, 
and even a large portion of the stem or trunk may be des¬ 
troyed ; and yet what remains of the plant may still live. And 




22 


HUMAN PHYSIOLOGY. 


Feeling. Motion. Sensitive plant and catch-fly. 

even more than this. A small portion of it may be made to 
take root and live by itself. It is not so with most animals. 
Mutilation can not be carried far without injuring some large 
organ which is essential to the life of the whole; and no part 
taken from its extremities can be made in any way to live by 
itself. 

27. Another obvious distinction is this. Animals are sen¬ 
tient and spontaneously-moving beings, while vegetables are not. 
The animal feels the action of agents upon it, and this it can 
not do without consciousness and thought. The evidences of the 
existence of consciousness and thought, and the consequent spon¬ 
taneous motion, are very slight in some animals. Still, there is no 
doubt of their existence in these cases. We see these evidences 
plainly in the great majority of animals; and we infer, very 
properly, the existence of sensation and thought in those excep¬ 
tional cases, where the evidences are doubtful or absent, as we 
find in them other marks of animal in distinction from vege¬ 
table life. 

28. The distinctions which I have mentioned are those which 
we see generally existing. Let us see how far they are essential 
and universal. 

29. The distinction in regard to locomotion, if we look at 
the animal as a whole, has its exceptions. There are some 
animals that are entirely confined to one spot during all their 
existence, as the coral animal and the sponge. But, while 
some animals are thus confined, they have the power of spon¬ 
taneous motion in some of their parts, which is exercised for 
the purpose of obtaining food, and, in some cases, for the 
avoidance of danger. This power is not possessed by any plant. 
Some few plants, as the sensitive plant and the Venus catch-fly, 
(dionsea muscipula,) exhibit a property which resembles it, but 
it is essentially a different thing. In these cases, the influence 
of the stimulus that excites the motion is communicated from 
particle to particle, from the point where the stimulus is ap¬ 
plied; and the motion is only in one direction, and not in 
various directions, as is the case with spontaneous animal mo¬ 
tions. This can be very readily seen, if we compare the motion 
of the sensitive plant or the catch-fly with those of the little fresh¬ 
water polype, called the Hydra. This animal, of which I give 
you here an enlarged representation, and also a representation 
of its natural size, is found in ponds. It attaches itself to any 
floating object—a stick or straw, as seen in the Figure—by a 
kind of sucker. Thus supporting itself, it stretches out its long 




DISTINCTIONS BETWEEN ANIMALS AND PLANTS. 23 


Digestive cavity. Nervous system. None in plants. 


arms, to take for its food any 
minute worm or insect which 
may float within their reach. 

When it catches one, it directs 
it to the mouth, a, which opens 
into the stomach or general cav¬ 
ity. Now, in doing all this, 
there is a variety, a compound 
character in the motion, which 
is in plain contrast with the 
simple motion of the leaves of 
the catch-fly and the sensitive 
plant. 

30. The distinction, in rela¬ 
tion to a digestive cavity, can 
not be made out in the case of 
some of the lower animals. And, 
if it could be, it is not an essen¬ 
tial distinction. For it only 
relates to a mere difference of 
arrangement in the absorbents 
that take up the nutritious substance in the two cases. The 
absorbents in the stomach of the animal, as before remarked, 
perform the same office that the absorbents do in the root of 
the plant. They only do it in a different place, and after a 
different manner. The same remarks, substantially, can be 
made in regard to the other large central organs which are 
found in most animals. 

31. The last of the distinctions, which I mentioned as being 
commonly observed, is really the essential distinction between 
plants and animals. I mean the capacity for sensation and 
spontaneous motion, which exists only in the animal. There 
is nothing truly analogous to this in the plant. And we, ac¬ 
cordingly, find a peculiar structure in animals, devoted to these 
functions, and others connected with them. This structure is 
the nervous system. No trace of such a structure has ever 
been discovered in any plant. If there were any true analogy 
between animal motion and the motions of the sensitive plant 
and the catch-fly, we should be able to find in them traces of ner¬ 
vous structure; for the structure of these plants is so plainly 
developed, that its constituent parts are easily distinguished. 

32. The nervous system is evidently not essential to nutri 
tion, for this is as well effected in the plant as in the animal. 


FIG. 1. 



HYDRA. 




24 


HUMAN PHYSIOLOGY. 


Thought and will. Instinctive and automatic motions. 

This is accomplished in both in substantially the same wa) 
The means by which it is done, and its arrangements are modi 
fied, as you have seen, in the two cases, to suit the differing 
circumstances. The nervous system, observe, then, is, for par¬ 
ticular purposes, superadded in the animal to what is common 
both to the animal and the plant, and so constitutes the essen¬ 
tial difference between them. And so, all the functions relating 
to nutrition, which are of course common to plants and animals, 
are called functions of organic life. But the functions which 
aA*e performed by the system superadded in the animal, the 
chief of which are sensation and spontaneous motion, are 
termed functions of animal life. These are sometimes also 
called functions of relation , from the especial connection which 
they form between the animal and all that is around him. 

S3. These animal functions, sensation and spontaneous mo¬ 
tion, imply thought and will. The order of action is this: 
sensation—thought in regard to it—action of the will in con¬ 
sequence of thought—then, from this action, an impression 
carried through nerves to organs termed muscles—motion in 
them from their contraction. This order, however, is not 
always observed. The first link, sensation, may be absent. 
Thought, without any preceding sensation, may prompt the 
will, and spontaneous motion results. The action of the will, 
too, may be left out, or may be in opposition. Thus, emotions 
may produce action of the muscles, the will not concurring, 
and perhaps opposing; as when we laugh at what is ridiculous, 
or weep at what is sad, in spite of restraining efforts dictated 
by the will. 

34. There are also instinctive motions, and motions which 
are termed automatic, with which the will has no direct con¬ 
nection. And the connection of sensation with them is, in 
some cases at least, doubtful. The action of the muscles, in 
swallowing, breathing, &c., and the action of that compound 
muscle, the heart, are examples of motions more or less dis¬ 
connected from the will, and also from sensation. The action 
of the heart is wholly removed from the direct influence of the 
will, and it is at least not obvious that it is influenced directly 
by sensation. It is influenced indirectly by both, through the 
agency of emotions awakened by them. The muscles of breath¬ 
ing, on the otheT hand, though ordinarily involuntary, may be 
directly influenced both by the will and by sensation. You 
can at will breathe faster and more deeply, and sensations of 
uneasiness in the chest modify the breathing. 




DISTINCTIONS BETWEEN ANIMALS AND PLANTS. 25 


Central organs of nervous system. Most enveloped in man. 

35. For all these different actions, thus produced in different 
ways, there are central parts of the nervous system upon which 
the causes of these actions produce the impressions or impulses 
from which the actions result. Thus, when a sensation is fol¬ 
lowed by a spontaneous action of muscles, an impression is 
conveyed by nerves to the central organ; the will there acts, 
and the impulse there given by this action of the will is car¬ 
ried by other nerves to the muscles, which execute the intended 
movement. 

36. These central parts or organs, which are the media, the 
instruments of impressions, are in different parts of the body 
of the animal; but the most important of them is what we 
call the brain. This part is developed most in those animals 
that give the greatest evidences of intelligence; and, therefore, 
it is more prominent in man than in any other animal. 

37. It may be remarked, as a general truth, that the nervous 
system, and its associate or subordinate system, the muscular, 
are developed in different degrees or forms, to suit the different 
characters and wants of animals. In man, the£ are more com¬ 
plex and perfect than in any other animal. The brain, in him, is 
a large organ, occupying the skull. The spinal marrow, and 
other central parts, and the nerves, are largely developed. And 
the muscles which are moved by this nervous system form a 
large portion of the bulk of the body. The organs of nutrition, 
analogous to those which make up nearly the whole of the 
plant, occupy the two cavities of the trunk of the body, the 
thoracic and the abdominal. But, as we descend in the animal 
kingdom, the nervous system becomes continually less promi¬ 
nent, and the system of mere nutrition more so. We at length 
come to animals, in which the nervous system is a mere small 
appendage to the system of nutrition, and only serves to direct 
the muscles in securing the food of the animal. In some of 

* these, we not only do not find a brain, but we fail to discover 
any traces of a nervous system. This is true of the Hydra, 
noticed in § 29. 

38. The nervous system, which so clearly distinguishes most 
animals from all plants, is fairly presumed to exist, though in 
an exceedingly slight degree, in those beings in which it can 
not be found, but in which we find other characteristics of the 
animal kingdom. And it is presumed, also, that the exercise 
of thought and the action of the will, which most animals so 
plainly exhibit, while they become less and less obvious a"* we 
descend in the scale, are not wholly obliterated in the very 

3 




26 


HUMAN PHYSIOLOGY. 


No nervous system in some animals; yet feeling and thought. 

lowest animals. It may, perhaps, be said, that as muscular 
action, as mentioned in § 34, is sometimes produced even in 
man without the intervention of thought or the will, it may be 
produced in animals of the lowest order altogether in this way. 
But we may more rationally infer that, as the chief object of 
motion in them is the securing of food, it is guided by the 
action of a will in obedience to their sensations. In other 
words, it is truly a spontaneous, and not a mere automatic mo¬ 
tion. And it is probable that there is in the very lowest of 
animals some degree, though it may indeed be slight, of enjoy¬ 
ment in the sensations received from the moving water about 
it, and from the satisfying of its wants in the process of nutri¬ 
tion. We will take the Hydra, a representation of which is 
given in Fig. 1, page 23, as an illustration of the above remarks. 
It is a minute gelatinous animal, in which no nervous or mus¬ 
cular fibres can be found. And yet it has an extraordinary 
power of extending and contracting itself. When it is alarmed, 
it draws in its arms, and shrinks into the form of a little glob¬ 
ule ; and if you should see it in this condition, you would not 
suspect that it had any arms or tentacula. But when it is 
searching for food, it often extends its body and its arms to a 
great length; and when it grasps its prey, it puts it into its 
stomach, which constitutes, so far as we can see, its whole 
body. We can not conceive of all these motions, thus exe¬ 
cuted to effect certain definite objects, without the agency of a 
will, and without sensations to prompt the will and guide the 
motions. The animal must have a power of choice, or it would 
put a bit of stick or straw into its stomach as readily as a 
worm or an insect. But the tentacula never grasp, among the 
various bits of things which float against them, any thing be¬ 
side the appropriate food of the animal. And it undoubtedly 
enjoys its food as really, though perhaps not as vividly, as any* 
human epicure; and has in some measure the same pleasur¬ 
able sensations which locomotion produces in us, as it floats 
along so quietly, with its arms hanging down from its body. 
Though there be no nervous fibres to be seen in the loose gela¬ 
tinous structure of this little creature, yet, as the phenomena 
which it exhibits are known to be produced by the nervous 
system in those animals whose structure is more plainly and 
thoroughly developed, we justly infer that there must be 
nervous matter, in some form, in this and other similar ani¬ 
mals. 

39. One more important distinction between animals and 






MAN IN HIS RELATIONS TO NATURE. 


27 


Peculiar endowments of man. Abstract reasoning. Conssience. 

plants remains to be noticed. It relates to tlieir chemical com¬ 
position. I stated, in § 23, that organized substances are com¬ 
posed mostly of four elements—oxygen, hydrogen, nitrogen, and 
carbon. Plants differ from animals, in having but little nitro¬ 
gen in their composition. It was formerly supposed that they 
contained none of this element. It is found only in particular 
parts of plants, as the seeds. We may regard carbon as the 
most characteristic constituent of vegetables, and nitrogen of 
animals. And in this connection it is interesting to observe 
that, while carbon is largely thrown off from the lungs of ani¬ 
mals, in the shape of carbonic-acid gas, it is as largely absorbed 
by the leaves of plants. Of this feet I shall take more par¬ 
ticular notice when I come to the subject of respiration. 


CHAPTER III. 

MAN IN HIS RELATIONS TO THE THREE KINGDOMS OF NATURE. 

40. Man is commonly spoken of as being at the head of the 
animal kingdom, and in the book of the naturalist is made an 
order of the class termed Mammalia. As the basis of the 
whole classification is mere material organization, and has no 
reference at all to mental or spiritual endowments, the classifica¬ 
tion, in regard to man, is in its principle correct. At the same 
time, it must be admitted, that it fails to recognize altogether 
the essential distinctions between man and other animals. 
These distinctions, making, as they do, a wide gap—“ an im¬ 
passable chasm,” as Professor Guyot expresses it—between man 
and the inferior animals, are to be found in certain peculiar 
spiritual endowments which man possesses. These I will no¬ 
tice now in the briefest manner, leaving it for another part of 
this book to treat more fully of this and other kindred subjects. 
One of these endowments is the power of abstract reasoning. 
Other animals in a certain sense reason, that is, they make in¬ 
ferences; but they never arrive at any general or abstract 
truths. Another endowment is a moral one, linking man in his 
spiritual nature to the Deity. It is conscience , or the knowledge 
and sense of what is right, in distinction from what is wrong. 
Other animals, in obedience to the passions of fear and love, 






28 


HUMAN PHYSIOLOGY. 


Immortality. Real relation to the animal kingdom. 


sometimes appear to the superficial observer to have an idea of 
what is right, as such; but there is not the slightest evidence 
that they really have any such knowledge. 

41. In view of these endowments of man, it is wrong to 
consider him merely as being at the head of the animal king¬ 
dom. He is something more than this. He is so much and 
so distinctly more, that the accepted classification of him, on 
the ground of mere difference of organization, gives a most 
inadequate idea of his true position in the scale of being. It 
leaves entirely out of view the essential distinctions; and it 
separates man from other animals, as you will see, by a distinc¬ 
tion of organization which is of rather a trivial, perhaps ques¬ 
tionable, character. 

42. The force of this view of the subject is enhanced, if we 
take into consideration that great fact, revealed to us by God 
in his Word, that man is destined to immortality. It may be 
objected that, as this fact is learned only by revelation, and not 
by observation, it is not to be regarded as a scientific fact. 
But, granting that there is truth in the objection, it certainly 
is allowable to allude to the revelations of Scripture, as con¬ 
firming or enforcing views developed by scientific observation. 
This is all that I have done in this case. The view which I 
have presented is based upon endowments that are recognized 
by the scientific observer, without the aid of revelation; and I 
appeal to the revealed fact of man’s immortality, as adding 
force to this view, and not as being at all necessary to the 
establishment of its truth. 

43. Let us look at this subject in another point of view. 
The grand essential distinction between animals and plants lies, 
as you have seen in the last chapter, in the fact that animals 
have a nervous system. Now, with this system, as you have 
also seen, appear certain mental manifestations. These differ 
widely in different animals, and are most prominent in those in 
which this system is most prominent and complicated. As we 
trace upward these complications, when we come to man, we 
find certain mental manifestations, which separate him by “ an 
impassable chasm” from all other animals. Till we arrive at 
him, the difference is one of degree, for the most part. But in 
his case it is a difference of kind, and a very wide one. Of 
such a difference the naturalist should certainly take very dis¬ 
tinct cognizance; and, if it be not consistent for him to do so 
in his classification, great force and prominence should be given 
to these views in his instructions on this subject. As the super- 




MAN IN HIS RELATIONS TO NATURE. 


29 


The hand of man. No other animal really has such a member. 

adding of the nervous system separates the animal from the 
plant, so, also, as Professor Guyot very justly maintains, the 
superadding of such endowments as we find in man separates 
him, by a chasm quite as “ impassable,” from other animals. 

44. The distinction commonly received as the ground of 
classification for man, I have said, is a trivial, perhaps a ques¬ 
tionable one. He is said to have two hands, and so makes the 
order Bimana; while apes and monkeys are said to have four 
hands, and are, therefore, considered as making the order 
Quadrumana. Now, if we observe carefully and fully the won¬ 
derful endowments of the human hand, we shall hardly be 
willing to allow that monkeys and apes have four such mem¬ 
bers. With a full view of the capabilities of the human hand, 
those members can not be considered as hands, but as members 
possessing some of the properties of both hands and feet. 
They are given to these animals to enable them to climb with 
facility, and to grasp their food; and they have none of that 
infinite variety of motion, which is so striking a peculiarity of 
the hand of intelligent man. The ground upon which they 
are said to have four hands is that which is thus stated by 
Cuvier. “ That which constitutes the hand , properly so called, 
is the faculty of opposing the thumb to the other fingers, so as 
to seize upon the most minute objects.” No animal besides 
man has this arrangement, except the Quadrumana. It is 
claimed, therefore, that they have hands, although they are 
very imperfect when compared with the hand of man. The 
imperfection is indeed so great, as to make us at least reluc¬ 
tant to admit the claim set up by the naturalist. “ While,” 
says Carpenter, “ the thumb in the human hand can be brought 
into exact opposition to the extremities of all the fingers, whe¬ 
ther singly or in combination, in those Quadrumana which most 
nearly approach man, the thumb is so short, and the fingers so 
much elongated, that their tips can scarcely be brought into 
opposition, and the thumb and fingers are so weak, that they 
can never be opposed to each other with any degree of force. 
Hence, although admirably adapted for clinging round bodies 
of a certain size, such as the small branches of trees, &c., the ex¬ 
tremities of the Quadrumana can never se:’ze any minute object 
with such precision, nor support large ones with such firmness, 
as are essential to the dexterous performance of operations for 
which the hand is admirably adapted.” Indeed, what is called 
the thumb of the Quadrumana is so short and slender, that Eus- 
tachius, the anatomist, very properly said that, regarded as an 




30 


HUMAN PHYSIOLOGY. 


Other peculiarities. Chin. Erect posture. Weeping and laughing. 

imitation of the thumb of man, it is a ridiculous affair. If 
then, we take into view the extensive and varied capabilities of 
the human hand, we must agree with Sir Charles Bell, when 
he says that “ we ought to define the hand as belonging exclu¬ 
sively to man.” This view of the subject has always impressed 
itself upon the minds of acute observers in all ages. Aristotle 
said, that man alone possesses hands deserving of the name. 
Anaxagoras said, that “ man is the wisest of animals, because 
he possesses hands.” And the opinion, thus uttered by these 
philosophers some centuries before the Christian era, is fully 
echoed at the present time. 

45. It would seem, then, that, if mere organization be ad¬ 
hered to, as the basis of classification, it is desirable that some 
ground of distinction in relation to man be fixed upon, which 
is more definite than the commonly received one. It is to be 
remembered, however, that, in classification, some one very ob¬ 
vious peculiarity that presents itself to the eye is ordinarily 
made use of as a mark of distinction, while accurate and full 
discriminations are followed out entirely separately from the 
mere classification. This is done in the case of man. His 
structure differs in many respects from that of the inferior ani¬ 
mals. It would make this chapter too long to point out all 
the differences. Some of them are important, while others are 
not. As an example of the latter, I will mention the fact, that 
no animal but man has a chin . Every other animal has its 
lower jaw retreating from the teeth, instead of projecting for¬ 
ward below, as in man. One of the most important and strik¬ 
ing peculiarities of man’s structure is that general arrangement 
which enables him to be in the erect posture. No other animal 
naturally assumes this posture, or is able to maintain it for any 
length of time; and most animals assume one which is en¬ 
tirely the opposite of this. Even the monkey, when taught by 
man to stand and walk, is by no means erect; but his lower 
limbs are crooked, and the moment that he escapes the neces¬ 
sity of being an imitator, he is on all fours. There is a distinc¬ 
tion of an interesting character, which concerns both the ner¬ 
vous and muscular systems. I refer to the fact, that no animal 
but man can shed team, or perform those muscular motions 
which are necessary to the acts of weeping and laughing. In 
view of this marked distinction, man has sometimes been desig¬ 
nated as “ a laughing and crying animal.” 

46. But the great essential distinctions, to which all the rest 
are really tributary, are, as I have before stated, of a mental or 




MAN IN HIS RELATIONS TO NATURE. 


31 


Tendency to skepticism. Robinet’s doctrines. 


spiritual character. And these should always be made peculi¬ 
arly prominent, whenever the distinctions between man and 
the inferior animals are treated of by the naturalist. This 
should be done, not only because they are essential, but also 
because, as I have just hinted, all other distinctions are subor¬ 
dinate and tributary to them. It is the mental peculiarities of 
man, for the most part at least, that render necessary those 
peculiarities which distinguish his organization from that of 
other animals. I will not dwell on this point, as I shall speak 
of it in another part of this book. 

47. In view of this whole subject, it may be said, that the 
classification upon which I have commented is not of itself of 
very great importance, provided that the definite distinctions, 
which have been pointed out as existing between man and 
other animals, be clearly recognized by the naturalist. The 
tendency, however, evidently is, to lose sight of these distinc¬ 
tions in the exclusive regard which is paid to mere material 
organization. This tendency, it is true, is effectually counter¬ 
acted in the case of the great majority of scientific men, by 
the comprehensive and Christian views which they take of the 
whole subject; but, still, it manifestly exists, and gives rise to 
many sceptical notions, especially in superficial and theorizing 
observers. Great care, Then, should be taken to oppose this 
tendency in all public teaching on this subject, whether it be 
done by books or lectures. 

48. There is a disposition, on the part of some writers, to 
obliterate the grand distinction between man and the inferior 
animals, and other distinctions which are stamped by the Cre¬ 
ator upon his works. Some go so far as to maintain, that there 
is not only no line to be drawn between the animal and the 
vegetable kingdoms, but none even between organized and un¬ 
organized substances. Robinet, and many other European 
authors, teach that all matter has living properties, and that 
every object that we see, whether mineral, vegetable, or animal, 
is the result of repeated and progressive efforts of nature. The 
ultimate aim of these efforts is considered to be the formation 
of man, who is looked upon as the perfection of organization 
evolved by these efforts. In advocating this theory, they make 
great use of resemblances and analogies, and even represent 
the fantastic shapes which minerals sometimes assume, from 
their slight resemblance to parts of the human body, “ as so 
many proofs,” in the language of Carpenter, 11 of this long and 
bungling apprenticeship of nature to man-making.” Although 




32 


HUMAN PHYSIOLOGY. 


Gradations in nature. Wrong ideas of perfection. 


such ridiculous doctrines are seldom formally advanced, there is 
a disposition in many scientific men to indulge in speculations 
■which have more or less resemblance to them. They seem dis¬ 
posed to confuse with the veil of mystic scepticism tae clear 
characters which God has imprinted upon the manifestations 
of his power. It is well, therefore, to fix these cnaracters 
definitely in the mind, in order to guard against the lascinating 
and bewildering speculations of a false science. A true science, 
forsaking the mazes of speculation, and inquiring oniy for the 
facts, reads with admiration and reverence the clear lines of 
God’s handiwork, and attributes to no imaginary agency, termed 
Nature, what bears the marks of exquisite design and Almighty 
power. 

49. An idea, somewhat akin to that of Robinet, is sometimes 
entertained, viz., that the varieties in the mineral, vegetable, 
and animal kingdoms are mere gradations in nature. There 
would be some plausibility in this notion if it were difficult to 
distinguish the minerals of the most perfect kind from the lowest 
plant, and then the plants of the highest order from the lowest 
animal. But the difficulty lies in other quarters. The most per¬ 
fect in the three kingdoms are distinguished from each other in 
the most marked manner; and it is only when the character¬ 
istic qualities are the least developed thatf there is any difficulty. 
One kingdom is a no more perfect formation than another. 
The crystal, with its exact lines and angles—the plant, with 
its curvilinear and less definite shapes—and the symmetrical 
animal, are equally perfect in their land. Each is made for 
a definite purpose, and is perfectly adapted to that purpose. 
In none is there any imperfection which could be remedied by 
endowments taken from another kingdom of nature. In the 
vast variety of forms which nature presents, there is to be seen 
no vain struggling after a higher and better state. There is no 
progressiveness, aiming at an ideal perfection. Neither are there 
gradations leading to it. All the works of the Creator are per¬ 
fectly adapted to the spheres which they fill. They were all, 
from “ man, made in His image,” down to the humblest ani¬ 
mal or plant, pronounced to be “ very good,” as they came 
from His hand. 

50. Let me not be understood to say that there are no gra¬ 
dations in nature. There are some of a very interesting char¬ 
acter ; but they do not obey any such laws as those which are 
indicated by Robinet and other fanciful theorizers. There are 
gradations in both the animal and vegetable world. You ob 




MAN IN HIS RELATIONS TO NATURE. 


83 


Man inferior to other animals in some respects. 


serve them as you go from the simplest plant up to the most 
complicated. And so of animals. But these two kingdoms 
of nature are separate in their gradations, and are not in one 
series together, as is represented by Robinet. And the grada¬ 
tion in each kingdom is by no means an unbroken and regular 
one, going up, step by step, from the lowest to the highest. 
For example, in the animal kingdom, there are not constant 
and regular additions made, as you trace the gradations up¬ 
ward. And though man stands at the top of the series, it is 
not as a compound, made up of all the excellencies found 
below him, with additional excellencies peculiar to himself. 
Superior as he is, as a whole, to all other animals, yet in some 
respects he is inferior to many of them. He is inferior to them 
in the wonderful capabilities of instinct. Some animals can do 
some things better than he can. The monkey is a better 
climber. Some animals can do what he can not. Birds and 
winged insects fly, but he can not. These points could I 4 
illustrated to any extent, but this will suffice. 

51. Man is often spoken of as being the most 'perfect of ani 
mals. This, as you will see from what was said in a previous 
paragraph, is not true in the strict sense of the word. His 
organization is more complicated, and he has more and higher 
endowments than any other animal; but the perfection of struc¬ 
ture, and of adaptation in contrivance to the purposes aimed 
at, is as manifest in all the varieties of animals as it is in 
man. 

52. In one respect, there is a gradation existing through tho 
three kingdoms of nature. It is in regard to formation or nu¬ 
trition. All the elements which are found in the composition 
of animals exist in the mineral world. But these elements, 
with very few exceptions, can not be transmitted directly to 
animals, but they are transmitted indirectly through vegeta¬ 
bles. No animal, therefore, can live on mineral substances, 
although these substances contain all the elements found in its 
composition. But vegetables draw their nutriment from the 
mineral world, and then furnish nutriment to animals. There 
is, therefore, in relation to formation, a gradation running 
through the three kingdoms, from the mineral up to the ani¬ 
mal. 

53. At the summit of the last step in this gradation stands 
man. To him, not only is the animal kingdom tributary, but 
so, also, are the mineral and vegetable kingdoms. They are all 
made for him, to beautify and gladden this his temporary home, 




HUMAN PHYSIOLOGY. 


8 i 

All nature tributary to man. Imperfectly so. 


and to sustain him in it. The subjection of them to him was 
undoubtedly perfect in his primeval condition of innocence in 
the garden of Eden. But now, we see this tributary subjection 
manifested only as a general fact, with many exceptions. These 
mark this life as the imperfect state, and this world as the 
temporary home of man, in which he can prepare himself 
for uhe perfect and everduring state and home of another life 
bevv.nd. 




PART SECOND. 

. CONTAINING, 

CHAPTERS. IV.—General Views of Physiology, with a Brief Account of some of th» 
Structures in the Body. CHAPTER V.— Digestion. CHAPTER VI.— Circulation. 
CHAPTER VII. —Respiration. CHAPTER VIII.— Formation and Repair. CHAPTER 
IX.— Cell Life. 


CHAPTER IV. 

GENERAL VIEWS OF PHYSIOLOGY, WITH A BRIEF ACCOUNT OF SOME 
OF THE STRUCTURES IN THE BODY. 

54. The contents of the previous chapters are preliminary 
to the consideration of the real subject of this work, the Physi¬ 
ology of Man. But they were necessary, in order to accomplish 
a very prominent object which I have in view. It is my wish 
that the student, as he examines the functions of the human 
system, should at the same time observe the analogies existing 
between man and other living beings, in the processes of life. 
He will, in this way, get an enlarged view of man in his rela¬ 
tions to the world around him, and will be prompted to observe 
the phenomena of life, in whatever department of nature they 
may be presented to his view. And, in order to promote this 
object effectually, I shall, as I proceed with the development of 
the physiology of man, refer occasionally to the analogous phe¬ 
nomena in other animals, and also in plants. This will serve 
to fix more definitely in the mind of the student the main facts 
that are to be communicated, at the same time that the bound¬ 
aries of his knowledge will be extended over fields full of in¬ 
terest. 

55. This is a work on Physiology, and not on Anatomy. 
Physiology treats of the offices or functions of the different 
parts of the structure, while Anatomy has regard to the struc¬ 
ture itself. In the following pages, I shall introduce the anat¬ 
omy of the system only so far as it is necessary to elucidate its 
physiology. 

Before proceeding to an examination of the individual sub¬ 
jects which will claim our attention, it will be proper to present 
some general views of them in their relations as a whole. 



36 


HUMAN PHYSIOLOGY. 


Natural division of the subject. Interest of the study. 

56. You have seen, in the preliminary chapters, that organ¬ 
ized living beings have much that is common to them all. This is 
true so far as nutrition is concerned. You have seen that the 
animal grows very much as the plant does, and that the 
arrangements for its growth vary from those of the plant only 
so far as the difference of the source of its nourishment, and of 
the circumstances under which it is obtained, require. The 
grand distinction, as you have seen, between animals and 
vegetables is to be found in the functions belonging to the 
nervous system. These functions are wholly separate from the 
nutritive functions, which animals perform in common with 
plants. 

57. This view of the subject suggests a natural division of 
the physiology of man into two parts, viz., the nutritive func¬ 
tions, and the animal functions, or those connected with the 
nervous system. In other words, the first division will com¬ 
prise all those subjects which relate to the building and repair¬ 
ing of the human structure; and the second will comprise those 
which relate to the uses for which the structure is made. The 
first class of subjects includes digestion, circulation, respiration, 
formation, and excretion. The second class includes locomotion, 
sensation, the five senses, the voice, instinct, thought, &c. 

58. The student will see at one glance, that a w r ide range of 
exceedingly interesting subjects opens before him. Contem¬ 
plated as a mere mechanism, the human system is full of won¬ 
ders. The principles of common Mechanics, of Hydraulics, of 
Pneumatics, of Optics, of Acoustics, are abundantly illustrated 
in the human body, by contrivances of the most exact and ex¬ 
quisite adaptation. But this congeries of beautiful mechanisms 
is all regulated by a nervous system, making it, by its minute 
fibris, to be alive with feeling in every part. Sensation and 
sympathy govern, through the nerves, in a wonderful manner, 
the ever-varying adjustments of all the parts of the complicated 
system. It is not only mechanism, but living mechanism, that 
develops to us its wonders, so numerous and diversified. And 
then, when we look at the soul—“that side of our nature 
which is in relation with the Infinite”—connected as it is by 
the nerves with every part of this mechanism, the interest of 
the study before us appears exceedingly great, and its variety 
never ending. The study is a peculiar one. It is not the body 
merely that you are to study in these pages; but it is the body 
and spirit united. The study differs from all others in this 
respect. In other studies, you look at either matter alone, or 




GENERAL VIEWS. 


37 


Bones. Two parts, animal and mineral. Cartilages. 

spirit alone; but here you look at them both, as brought to¬ 
gether in mysterious union. 

59. It will be proper, here, to say something in general of 
the structure of the human frame, before proceeding to a par¬ 
ticular view of individual subjects. I do this in order to avoid 
a frequent turning aside for explanation, which would not only 
be inconvenient, but would mar the interest of the study. It 
will not be necessary to go into a full description of the nume¬ 
rous and diverse textures, or tissues, (as they are commonly 
called,) of the body. I will notice only some of the principal 
of them. 

60. From the osseous or bony tissue, the solid part of the 
framework of the body is made. Bone is composed in part 
of animal matter, and in part of mineral. The mineral 
part is mostly phosphate of lime. These two parts of bone 
are in different proportions to each other in the different 
periods of life. The mineral part in the child is about one- 
half of the bone; in the adult, four-fifths; and in the old, 
seven-eighths. The bones are therefore very brittle in old age, 
while they are somewhat yielding in childhood. The mineral 
and the animal portions of bone can be separated from each 
other. If a bone be put into diluted muriatic acid, the mineral 
part will after a time become united with the acid, and the 
animal part will be left, having the perfect shape of the bone. 
Thus separated from the mineral part, it is so flexible, that it 
can be tied into a knot without affecting its shape. On the 
other hand, by subjecting a bone for some time to the action of 
heat, the animal part can be removed, and the mineral part be 
left by itself. 

61. The animal part of bone is cartilage, or gristle. This 
part is formed first, constituting a sort of mould, in which the 
bone is to be formed. The mineral matter is gradually depos¬ 
ited in the cells of the cartilage. In the very young child, you 
can see that this process is not completed, especially if you ob¬ 
serve the bones of the head. The bones are not united to¬ 
gether, as they are in the adult; and there is so little of mineral 
matter near their edges, that they can be bent with a very 
slight pressure. The proportion of mineral matter which is 
deposited in the cartilaginous bones varies much in different 
animals. In many fishes, there is almost none of this deposit, 
the skeleton retaining its cartilaginous character throughout 
life. 

62. Besides the cartilaginous portion of bones, there are car- 

4 




38 


HUMAN PHYSIOLOGY. 


Ligaments. Muscles. Tendons. Cellular tissue. 


tilages which are destined to remain so, instead of having 
mineral deposits made in their cells. The ends of the bones 
are tipped with them. They are placed between all the twenty- 
four bones of the spinal column. They form the connecting 
links between the breastbone and the ribs. Cartilage consti¬ 
tutes the body of the outer ear, of the eyelids, and of the 
lower part of the nose. The transparent part of the eye is 
formed of cartilage. This substance is placed wherever firm¬ 
ness and tenacity are required without hardness. 

63. The bones are united together by ligaments of various 
degrees of strength, according to the necessity of the case. 
They are moved by muscles, which, in man, are bundles of 
reddish fibres. Muscular substance is what is commonly called 
the meat in animals. It is of various colors in different ani¬ 
mals, or in the same animal at different periods of life. All 
motion in animals is produced by muscles. I will not go into 
an explanation of their action now, any further than to say, 
that they act by contracting or shortening their fibres. Com¬ 
monly there are tendons united with the muscles. These ten¬ 
dons are composed of strong white fibres, and have no power 
of contraction themselves. They serve merely as tlie cords 
by which the contracting muscles move the bones and other 
pails. 

64. The most common tissue in the body is what is called 
by the names, cellular membrane, cellular tissue, and areolar 
tissue. This last name is most commonly used by physiologists 
at the present time. The word areolar comes from the Latin 
w r ord areola , meaning a small open space. The term is appro¬ 
priate, because this tissue is filled with minute spaces or cells. 
The word cellular is quite as appropriate; and, as this will be 
more familiar to you, I shall make use of it whenever I shall 
have occasion to speak of this tissue. That you may under¬ 
stand what this tissue is, I will refer you to its appearance as 
you see it in different meats. It is the delicate white substance 
that you see between the different layers of muscle in a piece 
of meat. If you notice particularly, you will see that it is 
also between all the different fibres of the muscles. As the 
spaces or cells communicate together, butchers sometimes “ blow 
up ” this tissue in veal, in order to make the meat look more 
plump. This tissue is the universal packing material of the 
body. It is to be found almost everywhere. It surrounds 
every thing,—vessels, nerves, muscles, organs, &c. It enters 
into their composition, uniting together different tissues, and 





GENERAL VIEWS. 


39 


Communication between cells of cellular tissue. Shown in dropoy. 

also the fibres of the same tissue. It varies much in its com¬ 
pactness in different parts. It is very fine and compact where 
it is necessary that it should be so; while in other cases it is 
loose and delicate, allowing a free motion of the p>arts which it 
envelops and connects together. It is abundant an! loose 
among the muscles, and between them and the skin. Fig. 2 
represents a portion of cellu¬ 
lar tissue, inflated and dried, 
exhibiting the arrangement 
of its larger meshes. This 
is magnified twenty diame¬ 
ters. The free communica¬ 
tion which exists between 
the interstices or cells in this 
tissue is exemplified in drop¬ 
sy. These cells are bathed, 
in the healthy state, with a 
small amount of a watery 
fluid; and when this in¬ 
creases largely, forming the 
disease termed dropsy, it 
obeys the force of gravity in 
the cells, and accumulates 
most in the lowest parts of 
the lower extremities. This 
tissue is very elastic in health, 
so that if you press on the 
skin, there is no indentation left when the pressure is taken 
away, for the elastic cellular tissue at once rises from its state 
of compression, pushing the skin before it. But in dropsy it 
loses its elasticity by over distension; therefore there is pitting, 
as it is termed, after removing the pressure. We sometimes 
have an opportunity of seeing the communication between the 
cells manifested by the introduction of air into them. This has 
occurred in some cases in which an opening has been made, by 
disease or accident, from the air tubes in the lungs into the cel¬ 
lular tissue in the walls of the chest. The whole body has 
been seen largely swollen Jrom the air which has from this 
jjause accumulated in this tissue directly under the skin. 
Among the many tricks of impostors, the inflation of the cel¬ 
lular tissue of the head has been practised; and as it produces 
a frightful appearance, and therefore excites pity, the trick is a 
very successful one. 


FIG. 2. 



CELLULAR TISSUE. 





40 


HUMAN PHYSIOLOGY. 


Deposits of fat. Its uses. How kept in its cells. Mucous tissue. 

65. There are here and there in the cellular tissue deposits 
of fat. Various purposes are answered by these deposits. They 
are sometimes of use in promoting a free motion of the adja¬ 
cent parts. T^e eye has, intervening between it and the bony 
socket, a cushion of fat, on which it rests, and against which 
it is pressed when any violence is offered to it. Fat, as a non¬ 
conductor, is a protection against the cold, and it is therefore 
deposited largely in the cellular tissue under the skin, in ani¬ 
mals that inhabit cold climates. Fat, also, sometimes serves as 
nourishment to the system when its necessities require it. In 
diseases in which food cannot be taken in any amount, the 
fat is absorbed into the system. The heat of the body is 
maintained also, in part, by this process. This occurs in the 
torpid condition of hybernating animals. They commonly be¬ 
come very fat in autumn, as a preparation for the winter, and 
in the spring they come forth very lean, their store of fat having 
been used up for the purposes of nutrition and heat during 
their confinement. The fat thus deposited in the cellular mem¬ 
brane or tissue is not diffused merely in the interstices, but it is 
confined in cells of its own, which lie in these*interstices. Mi¬ 
nute blood-vessels pass from the fibres of the cellular tissue to 
these fat cells. The fat, which is an oily fluid, is kept from 
oozing through the pores of the cells that hold it by the blood, 
which is very nearly four-fifths water, and by the watery fluid 
which I have spoken of as bathing all the interstices of the 
cellular tissue; for oil, you know, will not pass through any 
porous substance that is wet with any watery fluid. If a por¬ 
tion of cellular membrane containing fat be dried, the fat, which 
in the moist state is wholly confined to its cells, now oozes 
through their pores. This is the reason that a lump of fat, as 
it is called, feels so oily after it has been exposed for a while to 
the air. 

66. The mucous tissue is that which lines all the cavities of 
the body that have outlets. It lines the mouth and the cavities 
of the nose, and descends into the lungs, the stomach, <fcc. It 
takes its name from the fluid called mucus , which is constantly 
secreted by innumerable minute glands, that are situated in the 
substance of this membrane. The chief object of this viscid 
fluid is to protect the membrane from the substances which 
come in contact with it, which would otherwise produce some 
irritation. This membrane is continuous with the skin, shading 
off into it insensibly, as you may observe on the lips. 

67. The serous tissue or membrane forms the outer coat or 




GENERAL VIEWS. 


41 


Serous membranes. Compound character of the organs. 


lining of nearly all those organs the inner coat of which is mu¬ 
cous membrane. This is the case with the lungs, the stomach, 
and the intestines. The serous membranes are white, smooth, 
and shining, and are lubricated with a watery fluid, called 
serum. Every serous membrane forms a cavity or sac without 
an outlet, differing in this respect entirely from the mucous 
membranes. Thus, in the case of the lungs, the serous mem¬ 
brane lining the outside of each of these organs passes from 
the lungs to the walls of the chest, lining the inside of them, 
and thus makes a sac without an outlet for each lung. This 
sac could be dissected off, and taken out whole. When the 
fluid which lubricates the inside of this sac increases to any 
extent, the disease called dropsy in the chest is produced. The 
membrane which thus lines the outside of the lungs and the 
inside of the walls of the chest is called the pleura, and it is the 
seat of the disease termed pleurisy. 

68. I have thus described some of the principal of the tis¬ 
sues which make up the human structure. The other tissues 
will be spoken of in the proper connection as we proceed. Be¬ 
fore dismissing this subject, I will call your attention to the fact, 
that the organs of the body are generally composed of several 
tissues united together. Thus, the stomach has three coats, as 
they are termed,—the mucous as the inner coat, the serous as 
the outer, and the muscular between them. And then we have 
the cellular tissue uniting these together. Besides these, there 
are arteries, and veins, and nerves, so that the stomach, which 
looks like a simple pouch, is really quite a composite thing. 
And the same can be said of the other organs. 

69. Before entering upon the particular consideration of the 
functions by which the system is built up and kept in repair, 
it will be well to take a general view of them, that you may 
see them in their connection and mutual dependence. Each 
of these functions has its special and appropriate part to play, 
in effecting the formation and repair of the structure. The 
material from which all parts of the body are formed and 
repaired is the blood. There are organs whose special duty it 
is to make this material; organs which distribute it; and or¬ 
gans which use it after it is distributed. There are also organs 
whose duty it is to receive the blood after it has been used, and 
fit it to be used again. This common building material of the 
body is made out of the food; and the succession of processes 
by which it is done I will describe in the next chapter. After 
it is made, it is distributed by the complicated apparatus of the 




42 


HUMAN PHYSIOLOGY. 


Summary of nutritive functions. Processes of digestion. 

circulation. This apparatus is therefore the common carrier of the 
building material of the system. It is the numberless little form¬ 
ative vessels, so small as to be invisible to the naked eye, that 
use the blood thus brought to them, and make and keep in 
repair all the various structures that we see in the body. When 
the blood has been used by these formative vessels, it is not fit 
to be used again until it is submitted to a purifying process by 
exposure to air; and to this particular object the lungs are de¬ 
voted. And besides all this, as there are continually some par¬ 
ticles which, in the wear and tear of the machinery, become 
useless, and even injurious, they must be got rid of in some 
way; and so there are organs for this purpose—organs of 
waste, as they are termed. It is also to be remembered, that 
the processes to which I have now alluded are so carried on, 
that the heat of the body, as will be fully explained hereafter, 
is steadily maintained. In the following chapters of this part, 
I proceed to a particular examination of the functions of which 
I have now given a brief summary. 


CHAPTER V. 

DIGESTION. 

70. I shall include, under the term digestion, all those pro¬ 
cesses which are necessary to effect the separation from the 
food of its nutritious portion, and the introduction of it into the 
circulation. A summary of these processes may be thus given. 
The food is broken up and ground in the mouth, and it is at 
the same time mixed with the saliva. It is then taken into the 
stomach, where it is kept in constant motion, and is under the 
solvent action of a fluid of a peculiar character. When it is 
brought into the right condition, it is passed from the stomach 
into the intestines. Here it is acted upon by two fluids, the 
bile, the secretion of the liver, and the secretion of another 
gland, the pancreas or sweet-bread. These secretions have 
some agency in separating from the mass its nutritious portion, 
and this is taken up or absorbed, in the form of a milky fluid, 
by little vessels lying on the surface of the inner membrane of the 
intestine. These vessels unite together to form a large tube, 
and through this the milky fluid is poured into the circulation, 
to replenish the blood. 






DIGESTION. 


43 


✓ 


Mastication. Teeth various, according to different kinds of food. 

Having given this summary of the processet which make up 
digestion, I proceed to speak of them more particularly in the 
order of their succession. In doing so, I shall notice some of 
the points in which other animals differ from man, in regard to 
these processes and the arrangements of the apparatus of diges¬ 
tion. 

71. Mastication is an important part in the process of diges¬ 
tion. The teeth, which perform this act, are very hard bodies. 
The body of a tooth is composed of two substances. The in¬ 
ner part is called the ivory, and the outer is called the enamei, 
which is exceedingly hard. The teeth are of different shapes 
for different modes of action. There are long and pointed 
teeth, for tearing; others, for cutting, which have a sharp edge; 
and others, for grinding, having for this purpose a broad and 
irregular surface. The teeth are differently shaped in animals, 
according to the kinds of food which they eat. Thus, the her¬ 
bivorous, or vegetable-eating animals, have grinding teeth to 
bruise their food; while the carnivorous, or flesh-eating animals, 
have sharp-edged teeth and long-pointed teeth, by which their 
food is torn and cut in pieces. And it is to be observed, that 
the movement of the jaws always corresponds with the char¬ 
acter of the teeth. In the carnivorous animals, the motion of 
the lower jaw upon the upper is a mere up-and-down, or hinge¬ 
like motion. As they have no grinding teeth, there is no 
need of any lateral or grinding motion. But in the animals 
that have grinding teeth, there is a lateral motion, to enable 
them to grind. You see this difference very plainly, if you ob¬ 
serve the dog and the horse while they are eating. In Fig. 3, 
you see represented the teeth of a carnivorous animal. The 
front teeth are long and pointed, for rending, while the back 


FIG. 3. 



TEETH OF CARNIVOROUS ANIMAL. 


FIG. 4. 



TEETH OF HERBIVOROUS 
ANIMAL. 






44 


HUMAN PHYSIOLOGY. 


Man an omnivorous animal. 

teeth have a sharp edge for cutting. In Fig 4, you see repre¬ 
sented the broad and irregular grinding surfaces of the teeth of 
herbivorous animals. In animals that live on insects, the teeth 
present conical points, which press into corresponding depres¬ 
sions in the opposite jaw, as represented in Fig. 5. In those 
that live on soft fruits, the teeth are rounded, as in Fig. 6. 
These are quite in contrast with the tearing teeth of the carniv¬ 
orous, and the grinding teeth of the herbivorous. 


fig 5. 



TEETH OF INSECTIVOROUS ANIMAL. 


FIG. 6. 



TEETH Or FRUGIVOROUS 
ANIMAL. 


72. There is an arrangement of the enamel and the ivory in 
the teeth of the herbivorous which ought not to pass unnoticed. 
Instead of having the enamel cover the ivory, as in the teeth 
of the carnivorous, the two substances are arranged in upright 
layers, as seen in Fig. 4. The object of this is plain. The 
ivory wears away faster than the harder enamel, and, therefore, 
the surface of the tooth always presents projecting hard ridges, 
fitting them for grinding thoroughly. A miller would say, that 
these are stones that never need picking. 

73. So perfect is the correspondence of the teeth with the 
kind of food on which the animal lives, that the skillful natural¬ 
ist can infer very correctly, from the examination of the teeth 
of an animal alone, the character of the food on which it lives, 
and even the general arrangement of its structure. As man 
has the three kinds of teeth which I have noticed, he is said to 
be omnivorous, or an eater of all kinds of food. In him, the 
front teeth are the cutting ones; what are called the stomach 
and eye teeth are the tearing ones; and the large back teeth 
are shaped for grinding. It will be observed that the tearing 
teeth, as they have not a very sharp point, and are no longer 
than the other teeth, have but little power when compared with 
the long and sharp tearing teeth of a carnivorous animal, as 
seen in Fig. 3. As man can make use of instruments to cut 








DIGESTION. 


45 


Whales have no teeth. Substitute for teeth in birds. 


his food in pieces, he does not need such power in his teeth as 
carnivorous animals have. Allowance should be made for this 
in estimating the amount of carnivorous adaptation in man. 

74. There are a few of the Mammalia that have no teeth. 
This is the case with the common whale. In his case, instead 
of teeth, there hang down from the upper jaw, as represented 
in Fig. 7, plates of a fibrous substance, called whalebone, which 
have their fibres separated at their free extremities, so as to 
make a sort of sieve. This is intended to catch the little gela¬ 
tinous animals, which the whale devours in great numbers. 


FIG. 8. FIG. 7. 



WHALEBONE. SKULL OF WHALE. 


For this purpose, he draws in the water, making it to pass 
through this sieve, and then expels it from the nostrils or blow¬ 
holes. Birds, too, have no teeth. Their place is supplied 
by a contrivance in the stomach itself, for the breaking up of 
the food. This will be described in another part of this 
chapter. 

75. While the food is cut and ground by the teeth, it is at 
the same time thoroughly moistened by the saliva, which is 
poured forth from certain glands in the neighborhood. There 
are three pairs of these glands. Fig. 9 shows the glands on 
one side. The parotid gland, 1, is the largest. This is situated 
in front of the lower part of the ear. It is the seat of the 
swelling in the disease called mumps. Its duct, 2, passes over 
one large muscle and between the fibres of another, and pours 
its contents into the mouth opposite the second small grinder of 
the upper jaw. If you press on this part of the cheek, you can 






46 


HUMAN PHYSIOLOGY. 


Formation of the saliva. Three pairs of salivary glands. 


FIG. 9. 



SALIVARY GLANDS. 


feel in the mouth an increased flow of the saliva. The sub¬ 
maxillary gland, 3, is situated inside of the lower jaw at its 
lower part; and its duct, 4, opens into the mouth at the side 
of the frsenum of the tongue. The sublingual gland, 5, lies 
under the tongue, and discharges its secretion by a duct at the 
side of that organ. These saliva factories, as we may term 
them, are in much more active operation at some times than 
at others. They are especially active when we are eating : and 
it is commonly estimated that, during an ordinary meal, about 
eight ounces of saliva are poured into the mouth. This large 
amount is wanted to moisten the food thoroughly before it is 
swallowed; and it is supposed, also, that it has some chemical 
influence in preparing the food for the action of the gastric 
juice in the stomach. More saliva than usual is needed, also, 
when we are speaking, in order to keep the parts properly lubri¬ 
cated, for the passage of the air in and out during speaking 
dries up the saliva by evaporation. And, accordingly, the mo¬ 
tion of the parts at such times stimulates a larger flow, j\ pt as 
pressure on the cheek will do it, as before remarked. Tjis 
result is favored by the arrangement of the duct of the parotid 
gland, which, as you have seen, passes over one large muscle, and 
then through the body of another. Chewing any thing excites 






DIGESTION. 


47 


Flow of saliva affected by sympathy. Swallowing. 


an increased flow of the saliva; and the tobacco chewer does a 
real injury to the salivary glands, by keeping them constantly 
in excessive operation, in addition to the ruinous effects of this 
drug on the system at large. When he eats, these over-worked 
factories can not turn out as good an article as they should, nor 
will it be in sufficient quantity. 

76. It is supposed that, besides the mere mechanical stimu¬ 
lus of the motion of the parts, the stimulus of sympathy is also 
concerned in exciting these glands to increased action. The 
glands are supposed to be affected in this way by the stimula¬ 
tion of the food on the surface of the mouth, about the orifices of 
their ducts. That sympathy does have an influence on their 
secretion is evident from the very familiar fact, that the thought 
of food will often, as it is expressed, cause the mouth to water. 

77. The fact, that these glands do not all secrete the same 
kind of fluid, has led to an interesting discovery in relation to 
them. The submaxillary glands secrete rather a viscid fluid, 
while that which is poured forth by the parotid and sublingual 
glands is perfectly limpid. Now, it has been found, by various 
observations and experiments on animals, that while the teeth 
are cutting and grinding the food, and the parotid and sub¬ 
lingual glands are pouring out the saliva to moisten it, no secre¬ 
tion comes from the submaxillary glands. But these gland*- 
pour out their viscid fluid the moment that the tongue thrusts 
the food back towards the throat, in the beginning of the acv 
of swallowing. The special object of this viscid fluid is then to 
cover the food, so that it may, to use a common expression, slip 
down easily into the stomach; and it has nothing to do with 
the moistening of the food, this being the particular office of 
the other two pairs of glands. 

78. When the food has been ground by the teeth, and 
moistened by the saliva, it is carried by the act of swallowing 
into the stomach. This act, simple as it appears to you, is a 
very complicated one, and is performed by the conjoined and 
agreeing action of many different muscles. The food is first 
thrust back over the surface of the tongue into the large cavity 
in the back of the throat, called the pharynx. In the pharynx 
are the openings of two tubes—the oesophagus or gullet, which 
is the passage into the stomach, and the trachea* or windpipe, 
the passage to the lungs. As the oesophagus lies behind the 


* This term is sometimes used, as here, to mean the whole of the tube conducting to 
the lungs, including the larynx, which is at the top of this tube, and sometimes it it 
estricted to that part of the tube which is below the larynx. 






48 


HUMAN PHYSIOLOGY. 


Parts employed in swallowing. Office of the epiglottis. 

trachea, the food, in passing to it, must go directly over the 
opening into the trachea. To prevent the food from entering 
the trachea, therefore, there is a little tongue-shaped body, 
called the epiglottis, extending back from the root of the tongue, 
and acting as a lid to the glottis, the opening into the trachea. 
When we are swallowing, this lid is shut down; but it is always 
raised up when we are breathing or speaking. When we swal¬ 
low, not only does the lid shut down, but the larynx rises to 
meet the lid, as you may readily perceive, if you place your 
fingers upon what is called Adam’s apple while you are swal¬ 
lowing. With the aid of Figures 10 and 11, all this will be 
very clear to you. In Fig. 10, you have a side view of the 
parts engaged in swallowing, as if the head were divided into 
two halves by a vertical section. At i, is the cavity of the nos¬ 
tril ; at h, are the lips; a is the divided bone of the chin; 
b is the tongue, between which and the spinal column, /, is the 
large cavity of the pharynx. In front of this cavity hangs the 


FIG. 10. 



VERTICAL SECTION OF THE THROAT. 


palate, g , as a door or valve, to direct the air coming from the 
trachea, d , either through the mouth or through the nost fils, 
according to its position. The oesophagus, e, is behind the tra¬ 
chea, and the epiglottis, c, shuts down when we swallow, to let 










DIGESTION. 


49 


Mode of action of the oesophagus in swallowing. 


the food pass over it into the 
oesophagus. In Fig. 11, you 
have a view of the same parts 
from the rear. At 1, is a sec¬ 
tion of the bones at the base of 
the skull; 3, 3, are the cavities 
of the nostrils; 2, 2, the walls 
of the pharynx spread apart; 5, 
the pendulous palate; 6, 6, the 
arch of the palate; 8, the root 
of the tongue; 9, the epiglottis, 
and 10, the glottis, or opening 
into the larynx; 13, the oeso¬ 
phagus; 14, the trachea. The 
pharynx, you see, is a funnel- 
shaped cavity, tapering down to 
the oesophagus, the opening of 
which is considerably below the 
opening of the trachea. 

79. When the food enters the 
oesophagus, it is carried through 
that tube into the stomach by the ac¬ 
tion of muscular fibres. These fibres 
are represented in Fig. 12. The cir¬ 
cular fibres are seen at a and b. These 
are removed at c, so as to show the 
longitudinal fibres. It is by the con¬ 
sent of action between these different 
sets of fibres that the food is propelled 
through the oesophagus. As the food 
descends, a dilatation of the circular 
fibres must everywhere take place 
where the food is, and a contraction 
of them immediately behind it—the 
dilatation making the way for it, and 
the contraction forcing it along. And 
in animals that chew the cud, these 
actions must be reversed when the ball 
of food is forced up through the oesoph¬ 
agus into the mouth. 

80. The food being introduced into 
the stomach, is here subjected to the 
action of the gastric juice. This is a 

5 


FIG. 11. 



VIEW OF THE THROAT FROM 
BEHIND. 

FIG. 12. 


(ESOPHAGUS LAID OPEN. 










50 


HUMAN PHYSIOLOGY. 


Gastric juice. Chemical in its action. 

peculiar fluid, somewhat acid in its character, which is secreted 
by very minute follicles, or bag-like cavities, situated in the sub¬ 
stance of the mucous membrane. Ordinarily there is none of 
this fluid in the stomach when there is no food there. Dr. 
Beaumont made some very interesting observations on this, as 
well as many other points, in the remarkable case which fell 
under his care. The individual, Alexis St. Martin, received a 
wound in his left side by the bursting of a gun. The wound, 
which opened into the stomach, never entirely closed, but an 
orifice remained, after the healing process had done all that it 
could. Through this orifice, Dr. Beaumont could look into the 
stomach, and observe what was going on there. He describes 
the mucous membrane, in its healthy state, as having a velvet¬ 
like appearance, with a pale pink color, and as being covered 
with a very thin, transparent, viscid mucus. On introducing 
some food, or irritating the mucous membrane mechanically, 
he saw, by the aid of a magnifying glass, “ innumerable lucid 
points ” projecting on the surface, and from these there exuded 
a pure, limpid, colorless fluid. These points were the follicles 
which secrete the gastric juice, now rendered turgescent by 
being stimulated to action. 

81. The amount of gastric juice secreted is generally about 
in proportion to the amount of food which the necessities of the 
system require. When the quantity of food taken is very 
much more than is required, there can not be a sufficient 
amount of gastric juice secreted to digest all of the food ; and 
some of the food must therefore remain undigested, and will prov6 
a source of irritation to the stomach. If the amount of food 
taken from day to day is not very excessive, but is only a little 
above the proper quantity, there will be enough of the gastric 
juice made to digest it; but the daily overtaxing of the pow¬ 
ers of the secreting follicles will, after a while, produce derange¬ 
ment in the stomach, and perhaps permanent disease. 

82. The action of the gastric juice upon the food is of a 
chemical nature. In order that it may act effectually on all 
portions of the contents of the stomach, this organ is kept in 
constant motion by the fibres of its muscular coat. These fibres 
are so arranged that, as they contract and relax, they keep up 
a sort of churning of the contents, and thus effect a thorough 
mixture of them with the gastric juice. In Fig. 13, you see 
these fibres represented. At 1, is the opening of the oesopha¬ 
gus into the stomach; and at 4, is the part which opens into 
the intestine. The fibres are in different layers, running in 




DIGESTION. 


51 


Churning of the food in the stomach. The chyme. 



FIG. 13. 


MUSCULAR FIBRES OF THE STOMACH. 

different directions. The outer peritoneal coat, 5, 5, is dissected 
off and turned back, showing some of the fibres that run length¬ 
wise of the organ, 6 ; and some of them transverse, V ; and 
others, 8, that run obliquely. You can readily see what effect 
the contraction of these different fibres will have on the shape 
of the stomach. The contraction of the longitudinal fibres, 6, 
brings the large, bulging end of the stomach, 2, and the small 
end, 3, nearer together. The transverse fibres, when they con¬ 
tract, diminish the capacity of the stomach transversely. And 
the oblique fibres modify these two motions by their oblique 
action. 

83. By the combined chemical and mechanical action of the 
stomach, its contents are, after a little time—in three or four 
hours—reduced to an uniform, greyish, semi-fluid mass, called 
chyme. While this process has been going on, the communi¬ 
cation between the stomach and the intestines has been entirely 
closed by a valve, called the pylorus. This is represented at 5, 
in Fig. 14, which presents a view of the inside of the stomach. 
This valve is made of a fold of both the mucous and muscular 
coats of the stomach. It is a very faithful sentinel, as is indi¬ 
cated by its name, which is derived from two Greek words, sig¬ 
nifying to guard the gate. It will not ordinarily permit any 
undigested food to pass it. While the process of digestion is 





52 


HUMAN PHYSIOLOGY. 


The pylorus. A sentinel. On duty only during digestion. 


FIG. 14. 



INTERIOR OF THE STOMACH AND SMALL INTESTINE. 


going on, the motions produced by the muscular fibres cause 
the contents to move about, and of course they are thrown 
against the pylorus, as well as any other part of the stomach. 
But the valve remains closed, until some portion comes against 
it that is thoroughly changed to chyme, and is therefore fit to 
pass on into the intestine. It then opens to let this pass, and 
it does so for any other portions that have become chyme. 
Toward the conclusion of the digestion of a meal, small quan¬ 
tities pass at first, and after a while, the contents pass quite 
rapidty through the valve. 

84. Although this sentinel-valve thus performs its duty so 
faithfully in relation to nutritive substances, it seems to let other 
substances pass very readily. Solid substances, swallowed by 
mistake, as buttons, pieces of money, the pits and skins of vari¬ 
ous fruits, often pass the valve without any trouble. The valve 
seems to be on duty as a sentinel only during the process of 
digestion; and, if the attempt to go through with this process 
prove unavailing, the pylorus, though it let such hard sub¬ 
stances as I have mentioned pass without difficulty, resists the 
passage of the undigested food, sometimes causing much un¬ 
easiness, and even perhaps pain, by so doing. In such a case, 
either the valve after a time gives over its resistance, or, hold- 









DIGESTION. 


53 


Theories of digestion. Eating between meals. Eating fast. 

ing out, tlie action of the stomach is reversed, and the offending 
matter is thrown off by vomiting. 

85. It is not a little amusing to read the different theories 
which were formerly broached to explain the process of diges¬ 
tion. Some supposed it to be a concoction , heat being, in. their 
view, the chief agent; some, a kind of putrefaction; some, a 
chemical solution; some, a trituration; and some, a process 
dependent upon the action of the nerves. Of these various 
theories, the celebrated Hunter playfully remarked: “ To ac¬ 
count for digestion, some have made the stomach a mill; some 
would have it to be a stewing-pot, and some, a brewing-trough ; 
yet, all the while, one would have thought that it must have 
been very evident that the stomach was neither a mill, nor a 
stewing-pot, nor a brewing-trough, nor any thing but a sto¬ 
mach. 11 All these theories are now done with; and it is pretty 
well ascertained, that digestion is a chemical process—in part a 
solution, and in part a fermentation—and that mechanical 
agency is employed only for the purpose of thoroughly exposing 
the food to the action of the gastric juice. 

86. The process of digestion, as it has been described, is a 
regular process, requiring a certain average period of time for 
its completion. If, during the progress of it, fresh food be in¬ 
troduced, its regularity is broken in upon, and the process fails 
to be well done. Then, too, if, immediately after the completion 
of the process, a new supply of food be taken, harm is done, 
because the organ has not its needed interval of rest. For 
these reasons, the practice of eating between meals is a very 
injurious one. Eating fast does harm, because,—1st, the food is 
not sufficiently ground; 2d, it is not mixed thoroughly with the 
saliva; and, 3d, more food is taken than would be sufficient to 
satisfy the hunger if the individual ate slowly, and, therefore, 
more than can be easily digested. Great variety in food stimu¬ 
lates the appetite unduly, and too much is consequently eaten. 
Exercise facilitates digestion, if it be not violent. An experi¬ 
ment was once tried upon two dogs, which was thought to 
prove that exercise hindered digestion. Two dogs were fed 
freely, and while one was left to lie still, tHk other was made to 
run about violently. Both dogs were kiPed after an hour or 
two, and it was found that, while digestion had gone on thor¬ 
oughly in the dog that was allowed to remain quiet, in the 
other the food was undigested. This only proved that violent 
exercise, taken immediately after eating, impedes digestion. It 
has been found, on the other hand, that light exercise pro- 

5* 




54 


HUMAN PHYSIOLOGY. 


Cause of hunger, state of the system. Its seat in the stomach. 

motes the process; and daily experience, among laborers, shows, 
that very strong exercise does not interfere with it, if a little 
Interval of rest be allowed, so that the process may be fairly 
begun. 

87. The sensation of hunger has been attributed to various 
causes,—as the empty state of the stomach, the presence of the 
gastric juice irritating the mucous membrane, <fee. It cannot 
arise from emptiness; for, if it were so, it should occur sooner 
than it does after eating, and it should not be absent in dis¬ 
ease, as it often is for a long time, when, the stomach is almost 
entirely empty. It can not arise from the irritation of the gas¬ 
tric juice ; for it was found by Dr. Beaumont, in his observa¬ 
tions of the stomach of Alexis St. Martin, that this fluid is not 
secreted till after food is introduced into the stomach. The 
cause of hunger is evidently in the state of the system. It is 
a state of want. Nutriment is needed by the formative vessels, 
the builders and repairers of the system, of which I shall speak 
particularly in the chapter on Formation and Repair. And 
they make their wants known as distinctly as the bricklayer 
does, when he calls for more brick and mortar. Through the 
nerves, an impression is communicated from these to the sto¬ 
mach, and the sensation of hunger is the result. That the sen¬ 
sation is seated there is evident from the fact, that it can be 
temporarily relieved by putting indigestible substances into the 
stomach. These produce the effect by causing other sensations 
there, which take the place, for the time being, of the sensation 
of hunger. After, however, the momentary effect is over, the 
sensation of hunger returns again in its full force. The cause, 
then, of the sensation is in the system at large, but its seat is 
in the stomach. Its degree of urgency depends upon this 
general state that causes it. If eating be delayed much beyond 
its usual time, or if the system has been exhausted by the wear 
and tear of severe labor, the sensation of hunger is very urgent. 
So, too, if disease has impoverished the system, as soon as the 
stomach is in a condition to respond to the call of the forma¬ 
tive vessels that set themselves to work to repair the waste, the 
hunger is often excetsive. Observe, here, that in order to have 
the sensation of hunger, not only must there be a want in 
the system at large, but the stomach must be in a state fitted 
to receive the notice of this want. And fortunately it is seldom 
m this state except when in a condition to do its work. If it 
were otherwise, food would often be introduced into it when it 
eould not be digested. The stomach is sometimes incapacitated 




DIGESTION. 


55 


Sensation of hunger affected by the mind. Thirst. 


for receiving the notice of the want of the system by mental 
* impressions. In this case, an impression is communicated from 
the brain to the stomach, through the nerves, which counteracts 
the impression conveyed from the system to this organ, and so 
n 3utralizes the sensation of hunger. Grief thus often destroys 
the appetite for food. One thing more is to be observed in 
relation to hunger. Although this sensation is caused by the 
want of the system, it is removed long before the nutriment 
reaches its final destination, and supplies the want. How is 
this ? It is either because the new sensations produced in the 
stomach, by the commencing process of digestion, take the 
place of the sensation of hunger, or an impression is sent all 
over the system from the filled stomach, which, so to speak, stills 
the clamor of want with the immediate prospect of a supply. 

88. Nearly the same remarks can be made in relation to 
thirst, that have been made in regard to hunger. The seat of 
this sensation is in the fauces or throat. Its cause is evidently 
not there; for the mouth and throat may be very dry, and yet 
there may be little or no thirst; while, on the other hand, there 
may be much thirst, although the mouth and throat are moist. 
The cause of the sensation is like the cause of hunger, in the *■ 
system at large; and, therefore, no local cause, producing a 
dryness of the throat, can cause thirst independent of a general 
condition. 

89. Before describing the remainder of the process of diges¬ 
tion, I will call your attention to the arrangement of the sto¬ 
mach, and the other organs of the abdomen engaged in this 
process. Fig. 15 exhibits them as they present themselves in 
a front view, except that they are somewhat separated from 
each other, instead of being as closely packed, as they are in the 
abdomen. The large end of the stomach, you see, lies to the 
left side,* and at this end is the spleen. The pancreas is be¬ 
hind the right end of the stomach. Above the stomach, and 
mostly to the right side, is the largest organ in the abdomen, 
the liver. It is represented as turned upward in the Figure. 
The stomach is directly connected with the small intestines at 
the pylorus. At the end of this long and winding tract begin 
the large intestines. The duct of the gall bladder, and that of 
the pancreas, empty their contents into the small intestine at its 
beginning. The office of the spleen has not yet been ascer¬ 
tained. Neither has that of the worm-like appendage at the 


* As this is a frojit view, the right side of the Figure is the left side ol the bodv 







56 


HUMAN PHYSIOLOGY. 


.Arrangement of the digestive organs. 


FIG. 15. 


CD 



GALL BLADDER. 


LARGE INTES—-- 
TINES. 

BEGINNING OF 
LARGE IN¬ 
TESTINES. — 

WORM-LIKE AP-— 
PENDAGE. 


-SPLEEN. 


LARGE INTES¬ 
TINES. 


-SMALL INTES¬ 
TINES. 


SMALL INTESTINES. 


DIGESTIVE ORGANS. 


beginning of tbe large intestines. The omentum, or caul, 
"which hangs like a curtain from the front part of the sto¬ 
mach down in front of the intestines, is not represented in the 
Figure. 

90. There is one arrangement in the abdomen which must 
not pass unnoticed. If the intestines were left to lie loose in 
this cavity, they would constantly be subject to disnlacement 
and injury. They are therefore fastened to the backbone by 
an arrangement, which secures them from any such accident, 
and at the same time allows of a sufficiently free motion of differ- 







DIGESTION. 


57 


The arrangement of the mesentery. Its offices. 


ent parts of this tube. It is this. The intestinal tube makes 
the margin of a broad sheet of membrane, the other edge of 
which is gathered up and fastened to thd spinal column. The 
arrangement is like a ruffle with a puffed edging. The mem¬ 
branous sheet is called the mesentery. As the intestinal tube, 
the puffed edging, is much longer than the ruffle itself, the 
mesentery, it is gathered on to the ruffle, as a seamstress would 
express it. Now, the mesentery is composed of two folds of 
the peritoneum, the smooth, shining, outer covering of the in¬ 
testines. The arrangement will be easily understood by the 
diagram in Fig. 16, which represents a section of the intestine 
with the mesentery. The cav¬ 
ity of the intestine, a, is lined 
by the mucous membrane re¬ 
presented by the inner circle. 

Next comes the muscular coat, 
and next the peritoneal, the 
outer, which, instead of making 
a circular tube, as the other two 
coats do, passes backward on 
both sides of the intestine, to 
make the mesentery, b. After 
being attached to the spine by 
means of cellular tissue, it is re¬ 
flected off to pass over other portions of the intestine, as seen at 
c, c. Between the two layers of the peritoneal membrane, in the 
mesentery, is considerable space, as seen at b. This space is 
filled up with blood-vessels, nerves, lacteals with their small 
glands, soon to be described, all bound together by the com¬ 
mon packing material of the body, the cellular tissue. You 
see, therefore, that the mesentery subserves more than one use. 
Besides fastening the whole tract of the intestinal canal to the 
spine, so as to guard it against accident, it acts as a secure 
medium for the communication of the blood-vessels and nerves 
with the intestines. And, besides, as you will soon see, it con¬ 
tains the little tubes which convey all the nutriment into the 
blood for the growth and repair of the body. 

91. I now go on to describe the remainder of the process of 
digestion. The chyme, (§ 83,) as it passes into the small intes¬ 
tine from the stomach, has mingled with it the bile and the 
secretion of the pancreas. These are poured into the mtestine 
at the point represented at 6, in Fig. 14. These secretions un¬ 
doubtedly have some agency in separating the nutritious part 


FIG. 16. 



PLAN OF THE MESENTERY. 




58 


HUMAN PHYSIOLOGY. 


Chyme. Chyle. Lacteals. Thoracic duct. 


of the chyme from that which is not so. When thus separat¬ 
ed, it is absorbed by the innumerable small vessels, called lac¬ 
teals, which are situaled in the mucous membrane. This nutri¬ 
tious part of the chyme is a milky fluid, called the chyle . The 
lacteals which absorb it are little tubes or ducts. These enter 
certain glands, called the mesenteric glands, for the purpose of 
having some effect, we know not what, produced upon it. They 
then pass on, as seen in Fig. If, to pour their contents into the 


FIG. 17. 


o 



* ORIGINS 
OF 

LACTEALS. 


SECTION OF INTESTINE SHOWING THE LACTEALS. 

thoracic duct. This duct, which is about the size of a common 
quill, running up on the left side of the aorta, the great artery 
of the heart, pours its contents into the junction of two veins 
at the top of the chest. As the circulation of the chyle in the 








DIGESTION. 


59 


Mecbunifiel contrivance of (lie thoracic duct Chyle makes blood. 


thoracic duct needs all the mechanical help that it can have, the 
mode of the joining of this duct with these veins is calculated 
to facilitate the freeness of the discharge of the chyle. As 
the two large currents in the veins, v and v, v , in Fig. 18, 


FIG. 18. 



JUNCTION OF THE THORACIC DUCT WITH THE VEINS. 

unite, there is created, by the forward motion of these cur¬ 
rents, a tendency to a vacuum at the angle at which they 
meet, the point where the thoracic duct, t, d, opens. There 
is, therefore, a suction power, as it is termed, exerted upon 
the fluid in this duct. The chyle, thus mingled with the 
blood, becomes a part of it. Or rather, I should say, that the 
blood is made from the chyle, and, as it is constantly used for 
formation and repair in all parts of the system, it is thus as 
constantly replenished. The material by which all the textures 
of the body are madfe and are kept in repair, is furnished to 
the system through this small duct, in the form of a milky 
fluid. You observe in Fig. 17, certain lymphatic vessels. These 
are trunks of absorbents, hereafter to be spoken of particularly, 
which bring a fluid called lymph , to be mingled with the chyle, 
and to be poured with it into the circulation. 

92. The extent of surface on which the absorbent lacteals 
open can not be appreciated, if you look merely at the outside 
of the small intestines. It can be done only by looking at the 
inner mucous coat. This coat is really much more extensive 
than the outer coat, or the middle one, the muscular, and it is 
full of folds, as represented in Fig. 14, on page 52. The ob- 






60 


HUMAN PHYSIOLOGY. 


Extent of absorbing surface in intestines. Alimentary canal in different animals. 

ject of this is to offer a very large absorbing surface to the 
chyme as it passes, and also to prevent its passing along as 
rapidly as it would if the mucous surface were perfectly smooth, 
instead of having folds. Before leaving this subject, I would 
again call your attention to the analogy which exists between 
absorption in animals and in plants. The lacteals do for the 
animal in its stomach, what the absorbents do for the plant in 
the extremities of its roots. Both absorb and assimilate nutri¬ 
ment. The function is the same. It differs in the two cases 
only in the circumstances under which it is performed. 

93. The digestive apparatus varies much in different animals, 
according to the kinds of food on which they live. As a gene¬ 
ral rule, the more the food differs in character from the animal 
itself, the more complicated and extensive is the apparatus. 
Thus, the herbivorous animals have a very long alimentary 
canal, and the beginning of it, the stomach, is a complicated 
organ. While, on the other hand, in the carnivorous, the flesh 
which they eat being very much like their own flesh, and, there¬ 
fore, not requiring very much of a process of assimilation, the 
stomach is a simple organ, and the alimentary canal is very 
short. In the sheep, for example, the alimentary canal is about 
twenty-eight times the length of the body, but in the lion it is 
only three times its length. In man, who lives on a mixed 
diet, the alimentary canal is about six times the length of the 
body. 

94. The stomach is more complicated in animals that chew 
the cud than in any other animals. It has four distinct cavities, 
and, as you will see, a singular mechanism is called into opera¬ 
tion in managing the food as it passes through them. In Fig. 
19, you have a representation of the stomachs of the sheep, as 
they appear exteriorly. The course which the food pursues is 
this. As the animal crops the food, it passes into the first sto¬ 
mach, which is little else than a great reservoir to hold it and 
to soak it. Then it passes into the second stomach, from which 
it is returned into the mouth. On being swallowed again, it 
passes from the oesophagus into the third, and thence into the 
fourth stomach. In Fig. 20, you see the interior of these four 
stomachs; and by the aid of this I will describe the process of 
digestion in the sheep more particularly. You see the very 
large first stomach, or paunch, in which the food is accumu¬ 
lated. It is not yet masticated thoroughly, for the animal has 
swallowed it as fast as he could, and packed it away in this 
reservoir. From this it is passed, in small quantities at a time, 




DIGESTION, 


61 


Digestion in the sheep. 


FIG. 19. 



(ESOPHAGUS. 


ORIFICE OF 
STOMACH. 


3d STOMACH 


INTESTINE. 


CD 

Pi 

53 

O 

H 

o 

GQ 

i3 

S3 

> 

P 4 

E-* 




STOMACHS OF THE SHEEP. 


FIG. 20. 



(ESOPHAGUS. 

GROOVE. 

MANYPLIES. 

REED 


INTERIOR OF THE STOMACHS OF THE SHEEP. 


into the second stomach, the honey-comb , so called from the 
peculiar network of folds in it. Here the food is rolled up into 
balls by the action of the muscular fibres in this network. 

6 
















62 


HUMAN" PHYSIOLOGY. 


Digestive apparatus in birds. Different in the grain-eating and the flesh-eating. 

Each ball of food is passed up through the oesophagus into the 
mouth, where it is chewed and thoroughly mixed with the saliva, 
in doing which the animal seems to have great enjoyment. 
Then it is swallowed, and, as it passes from the oesophagus, in¬ 
stead of going into the paunch, as it did when swallowed the 
fiist time, it is directed through the groove seen in the Figure 
into the third stomach, the manyplies. This has many folds, 
like the leaves of a book, so that the food is exposed to a large 
surface in this cavity. It passes from this to the fourth sto¬ 
mach, the reed. Here, and here only, it is acted upon by the 
gastric juice. This, therefore, is the true stomach, all the other 
cavities furnishing only preparatory steps to the true process of 
digestion. It is from this fourth stomach that what is called 
the rennet is taken. When fluid matter is swallowed, it goes 
directly into the second stomach, and not into the first, the 
paunch; so that, in the case of the sheep, the drink goes one 
way, and the solid food another. And, what is still more singu¬ 
lar, while the animal is a suckling, the milk passes directly into 
the fourth stomach through the third, which has its folds so 
closed together as to form a mere tube to conduct it to its des¬ 
tination. And the great paunch and the honey-comb are 
wholly useless until the animal begins to crop its food for 
itself. 

95. In birds, the digestive apparatus is necessarily very 
peculiar, from the fact that they do not masticate their food. 
They have, on this account, an arrangement in the stomach 
itself for grinding the food. In the cavity called the gizzard 
are two opposing surfaces, made very hard, so that by rub¬ 
bing together they bruise the grains; and while they are 
thus ground, as between two millstones, the gastric juice 
is poured down upon them from above. This arrangement is 
seen in Fig. 21, which represents the digestive apparatus in the 
turkey laid open. At b is the gizzard, showing the two hard 
surfaces, which are rubbed together by the stout muscles that 
make the great bulk of the organ. Above, at a, are the 
glands which pour forth the gastric juice. And above this 
part of the stomach there is, in all grain-eating birds, a large 
sac bulging out from the oesophagus, called the crop, which is 
a reservoir for the food, just as the paunch is in the ruminating 
animals. In those birds that live on flesh or fish there is no 
nuch grinding apparatus; and the walls of the stomach are 
«'uite thin, and it presents no hard surfaces. 

96. It would be interesting, were it consistent with the plai: 




DIGESTION - . 


68 


digestion in the turkey. Digestive apparatus in different animals. 


FIG. 21. 



STOMACH OF THE TURKEY'. 


of this book, to go into a further examination of the varieties 
in the digestive apparatus in different animals. They have a 
very wide range, being according to the wants of the animal in 
each case. The kind of food, the mode of life, and the pur¬ 
pose which the animal is designed to fulfill, are the circumstances 
which govern these variations. The proportion which the di¬ 
gestive apparatus bears to other parts varies very much; and 
in some of the lower orders of animals, the body seems to be 
all stomach. In such cases, the only appendages are those which 
seize the food and direct it into the orifice of this organ. This 









64 


HUMAN PHYSIOLOGY. 


Apparatus of the circulation. Heart, arteries, veins, capillaries. 

is the case with the hydra, represented in Fig. 1. And, what 
is very singular, the outside of the body of this animal is just 
as capable of acting as a stomach as its inside. For you may 
turn it inside out, as you can a stocking, and yet it will go on 
to catch and digest its food as usual. But, wide as the varia¬ 
tions are in the digestive apparatus of animals, the same com¬ 
mon object is aimed at in all—the assimilation (§ 10) of nu¬ 
trient substances to the animal, to produce a material from 
which its structure can be built and kept in repair. There is, 
therefore, much that is common to them all in the modes in 
which this object is accomplished. And even the analogy 
which exists between the animal and plant, in regard to assimi¬ 
lation, does not relate to the fact alone, but in some measure to 
the modes in which the process is effected. 


CHAPTER VI. 

CIRCULATION OF THE BLOOD. 

97. In the last chapter I described the manner in which tne 
blood is made from the food. The blood, thus prepared, is 
circulated in every part of the body, that it may be used for 
the purposes of construction and repair. The apparatus by 
which this is done acts, as I have before said, as the common 
carrier of the material which is used everywhere in the body 
by the laborers, the builders, to whom it is thus brought. 

98. This apparatus consists of several parts—a great central 
organ, the heart, situated in the chest; the arteries, the tubes 
by which the blood is conducted to all parts of the body ; the 
veins, other tubes, which bring the blood back to the heart; 
and capillaries, a network of exceedingly minute vessels, through 
which the blood passes as it goes from the extreme arteries into 
the beginnings of the veins. The blood goes from the heart 
through a large artery, called the aorta, which sends forth 
branches; and these divide and subdivide, so that the extreme 
arteries, through which the blood flows into the capillary net¬ 
work, are very minute. And the veins which receive the blood 
from this network to carry it back to the heart, are equally 
minute; but joining together more and more, as they proceed 





THE CIRCULATION. 


65 


Heart a forcing and suction pump. Arteries firm tubes. Why. 

toward the heart, they are at length all united into two great 
venous trunks, one from above and the other from below, which 
pour their contents into this organ. The capillaries, taking 
their name from the Latin word, capilla, a hair, are so small 
that they can not be seen by the naked eye. In any small 
cut, the blood which oozes out comes from multitudes of these 
vessels. They serve to hold the blood, while the formative ves¬ 
sels, that construct and repair the body, may select from it such 
materials as they need for their purposes. 

99. The heart is a great central forcing and suction pump, m 
the midst of this circulating apparatus. When it contracts, it 
forces the blood out through the aorta and its branching ar¬ 
teries into all parts of the system. And when it enlarges or 
dilates itself, it, by suction, as it is termed, receives the blood 
returning from the system through the veins. The blood never 
ceases to go these rounds. The necessity for this continual 
motion you will perceive as I proceed with the development of 
the subject. 

100. The arteries differ from the veins in their structure and 
arrangement. The arteries are firm tubes, while the veins are 
lax in their structure. The object of the difference is obvious. 
As the blood is forced into the arteries by the powerful action 
of the heart, it is necessary that they should be strong and 
firm, else, they would be liable to dilatation and rupture, and 
death would frequently result. As it is, it is not a common 
event to have an artery dilate and burst, though it does occa¬ 
sionally happen. When dilatation does occur in an artery, it 
is called an aneurism. But the arteries need to be firm, not 
only for the sake of security against rupture, but also that the 
force of the heart may propel the blood to the extremities of 
the arterial system. If the arteries were lax tubes, like the 
veins, the impulse would soon be lost in the yielding tubes, and 
the blood would move very sluggishly in the small arteries at a 
distance from the heart. What we call the pulse, is caused by 
this impulse. If the arteries were lax tubes, the pulse would 
not be felt at any great distance from the heart. Instead of 
being distinct, as it now is, with every beat of the heart almost 
to the very extremities of the arterial system, it would be ren¬ 
dered confused by the yielding of the tubes, even quite near 
the heart, and at a distance from that organ it would be en¬ 
tirely lost. 

101. Besides the firmness of the arteries, there is another 
circumstance which favors the freeness of the flow of blood 

6 * 




66 


HUMAN PHYSIOLOGY. 


Different arrangement of arteries and veins. 

through them. It is their mode of division. The branch of 
an artery leaves the main trunk at a sharp angle, making thus 
only a slight deviation from the direction of the current; while, 
on the other hand, in the veins where the current flows in an 
opposite direction, the branch unites with the trunk at nearly a 
right angle. This difference is represented in Fig. 22 ; 1 being 
the artery, and 2 the vein. 


FIG. 22. 

1 2 



ARTERY AND VEIN. 


102. The venous system has a much greater capacity than 
the arterial. That is, all the veins of the body are together ca¬ 
pable of holding more blood than all the arteries are. And the 
blood moves very rapidly and directly from the heart through 
the arteries, but it comes back to the heart quite slowly through 
the veins. Every thing is arranged to promote this rapid cir¬ 
culation through the arteries, while the venous system is calcu¬ 
lated for a slow but sure progress of the blood back to the 
heart. To secure this, valves, made of folds of the inner lining 
of the veins are so arranged as to prevent the blood from flow¬ 
ing in the wrong direction. Fig. 23 represents a vein cut open 
so as to show these valves. A shows the valves as they appear 
when the vein is laid open and spread out; B, as they appear 
when the vein is simply laid open; and C represents the ap¬ 
pearance of the outside of the vein where there are valves. 






THE CIKCULATIOJST. 


67 


Valves in veins. Dangerous to wound an artery. Therefore well guarded 


FIG. 23. 



VALVES IN THE VEINS. 


The need which there is of this help to the circulation through 
the veins is obvious. The suction power of the heart is not 
competent, unaided, to move the blood throughout all the lax 
venous system. These pocket-like valves, therefore, are made 
in the veins to assis' ’.he circulation there. They do so in this 
way. Every motion of the muscles or other parts about the 
veins tends to keep the blood in motion, and the valves serve to 
prevent this motion from being in the wrong direction. The 
difference in force and velocity with which the blood moves in 
the arteries and in the veins, is made manifest when they are 
wounded. The blood flows from a wounded vein in a slow 
and steady stream. From an artery it flows rapidly, showing 
the impulse of the heart in its jets, which correspond exactly 
with the pulse. Hence comes the danger in wounding an ar¬ 
tery, while the wound of a vein is ordinarily attended with no 
danger. Accordingly, we find that the “Maker of our bodies” 
has so placed the arteries that they cannot easily be wounded, 
while many of the veins are quite freely exposed. The arteries 
are deeply seated, except in some few cases where this is im¬ 
possible ; but the veins are often superficially situated. You 
can see this, for example, in the bend of the arm. Some large 
veins appear there just under the skin, while the artery which 
supplies the arm is imbedded among the muscles and tendons. 
In every part of the body, the most secure spot is chosen for 
ra artery. Thus, at the knee joint, the artery, instead of run- 
ng over the surface of bone, where it would be liable to be 

















68 


HUMAN PHYSIOLOGY. 


Few arteries superficial. Mode of stopping the bleeding of an arterv 

■wounded, lies deep in the ham at the rear of the joint. The 
same is true of the elbow joint, just alluded to, and of other 
parts of the body. Although there are arteries everywhere, 
they are so uniformly deeply seated, that it is only in a few lo¬ 
calities that you can readily find one. You can feel one pul¬ 
sating at the wrist, and also on the temple. Here the arteries 
are superficial, only because it is impossible that it should bo 
otherwise. 

103. When the physician bleeds a patient, he commonly 
does it at the bend of the arm, as being the most convenient 
place for the operation. A ligature of some sort, as a ribbon, is 
tied around the arm above the elbow, with sufficient tightness 
to interrupt the flow of blood toward the heart in the super¬ 
ficial veins, but not so tightly as to prevent the free supply of 
blood to the arm by the artery. It is commonly tied as tightly 
as it can be without stopping the pulse at the wrist. An open¬ 
ing is then made in one of the veins; and, as the blood flows 
freely into the arm from the heart through the artery, on its 
return, so much of it as passes through the opened vein is dis¬ 
charged at that point. 

104. It will be proper here to give some practical instruc¬ 
tion, in regard to stopping the flow of blood from a wounded 
artery, as many lives have been lost from the ignorance of by¬ 
standers when such accidents have happened. Enveloping the 
part in cloths, which is so commonly done at such times, does 
no good, but only serves to catch and conceal the blood as it 
flows. Pressure upon the artery, on that side of the wound 
which is toward the heart , will of course interrupt the supply of 
blood from this organ to the wound. Firm pressure with the 
thumb will do it. But the pressure must be made at the right 
point, that is, directly upon the artery. You may not, in all 
cases, press upon the right spot at once. If you do not, the 
blood will continue to flow. In this case, press at different 
points, until you find the point at which you see that pressure 
stops the flow of blood from the wound. But you may not be 
able to find the right spot. If you can not, you can tie a slip 
of strong cloth or a handkerchief around the limb, above the 
wound, and twist a stick in it until the bleeding stops. In one 
or the other of these ways, you can prevent the loss of blood 
until the surgeon arrives to take charge of the case. 

105. Although there is no such free communication between 
arteries as exists between the capillaries, there is some amount 
of communication, and particularly in certain parts of the body 




THE CIRCULATION. 


69 


Aneurism. Communication between arteries. 


And it is well that it is so, for it sometimes helps the surgeon 
to save a limb, when he could not do it if there were no com¬ 
munication. I have already alluded to a disease of the arteries 
called aneurism. An artery has three coats, one of which is a 
strong fibrous one. When this is thinned or ruptured, the 
other two coats bulge out, forming a pulsating tumour. And, 
as the blood is constantly pumped into this by the force of the 
heart, it enlarges, and at length it may burst, and the life of 
the patient will be destroyed by the loss of blood. When an 
aneurism formed in a limb, as for example in the ham, the sur¬ 
geon, in former times, used to save the life of the patient by 
amputating the limb above the aneurism. Putting a ligature 
round the artery above the aneurism would of course stop the 
flow of blood into it; but it was supposed that the limb would 
die, in that case, from the want of a proper supply of blood. 
But it was found, at length, that this was not so; and surgeons 
now, m such cases, cure the disease, and save the limb too, by 
tying the artery. Immediately after the operation the limb is 
cold, and there is plainly very little circulation in it. But in a 
few hours the circulation becomes free, and in a little time it is 
as well established as ever. This is effected by the communi¬ 
cations which exist between the branches which go off from the 
artery above the aneurism, and those which go off below it. 
It is obvious, however, that this would not be thoroughly 
effected if no change took place in the size of the communicat¬ 
ing arteries. But this change does occur. Some of them be¬ 
come enlarged to meet the necessity of the case. This is a 
most interesting fact; and so is also the fact, that these commu¬ 
nications between branches of arteries are very common in the 
neighborhood of those places in the body, where aneurism, 
from strains produced by violent and sudden motion, is peculi¬ 
arly apt to appear. This same provision avails, of course, when 
aneurism is cured by pressure made upon the artery above it, 
a measure which modern surgery has found in many cases to 
be as effectual as tying the artery. 

106 . There have been great differences of opinion among 
physiologists, in regard to the proportionate amounts of agency 
that the different parts of the apparatus have in carrying on 
the circulation. The heart manifestly exerts the chief agency, 
both by its forcing and its suction power. You can get a clear 
idea of the manner in which it exerts these two forces in this 
way. Fill a ball of India rubber, to which a tube is attached, 
with water, and immerse the tube in water in a vessel. If you 





70 


HUMAN PHYSIOLOGY. 


Action of the heart illustrated. Agency of the capillaries in the circulation. 

press the sides of the ball together, some of the water is forced 
out into the vessel. This represents the contraction of the 
heart. If, now, you allow the ball by its elasticity to resume 
its round shape, the water rushes into it from the vessel. This 
represents the dilatation of the heart. The dilatation of the 
ball results from its elasticity; and so it is supposed by some 
that the dilatation of the heart results from the same cause, its 
contraction alone being produced by muscular action. Whether 
this be so or not, the dilatation is an active one, and the blood 
rushes into the heart from the veins by suction, as it is termed. 
The dilatation is so active that, as has been shown by experi¬ 
ments on animals, even a great amount of pressure is not able 
to prevent its taking place. 

107. But, great as the agency of the heart is, it is not true 
that it is the only moving power, and that the arteries and veins 
are mere passive conducting tubes. There are various phenomena 
which show that the arteries, the capillaries, and even the lax 
veins, exert a considerable agency in circulating the blood. I 
will merely allude to some of these phenomena. Determina¬ 
tions of blood to particular parts show that the blood-vessels 
have an active agency in the circulation. In inflammation of 
any part, there is an increased activity of the particular portion 
of the circulating apparatus supplying that part. In the act of 
blushing, there is a local activity of the circulation somewhat 
independent of the heart. This is also true of the circumscribed 
flush of hectic. 

108. There is one portion of the circulation in which the 
active agency of the capillaries is especially manifest. The 
veins, as I have told you, receiving the blood from all parts of 
the body, at length are all united into two veins, which empty 
their contents into the heart. But there is a very remarkable 
exception to this. The veins which collect the blood from the 
viscera in the abdomen unite in one large trunk, called the vena 
portae; and this, instead of pouring its contents into the large 
vein that goes up to the heart, divides, like an artery, into 
branches, which take all this blood to the liver for the manufac- 
ti re of bile. Fig. 24 represents this circulation of the vena 
portae. 1, 1, are the veins coming from the intestines ; 2 is the 
trunk of the vena portae ; and 3, 3, are the branches of it dis¬ 
tributed in the liver. Now, it can not be pretended that the 
suction power of the heart extends its influence through the veins 
that bring the blood from the liver, then through the capillaries 
of this organ, and then through all the veins that bring the 




THE CIRCULATION. 


71 


Circulation in the liver. Why the veins are full and the arteries empty after de&ik. 


FIG. 24. 



CIRCULATION OF VENOUS BLOOD IN Tlite LIVER. 

blood to the liver, even to the capillaries of the abdominal vis¬ 
cera. There must be, in this case, some propelling power in 
the capillaries, and some, too, also in the veins. If there were 
not, another subordinate heart would obviously be needed in 
the vena portae, to pump up the blood from all the veins of the 
abdominal viscera, and then to send it through all its branches 
into the capillaries of the liver. 

109. The veins have a less active agency in the circulation 
than any of the other parts of the apparatus. It is for this 
reason that commonly after death the veins are found quite 
full of blood, while the arteries are nearly empty. The appa¬ 
ratus of the circulation may be regarded as forming a circle of 
organs in this order—the heart, the arteries, the capillaries, and 
the veins. The blood is constantly going the rounds of this 
circle. It is plain that, as the apparatus is about to stop, there 
must be an accumulation in the weakest, least active, and most 
relaxed of this circle of organs. The arteries and capillaries force 
the blood into the veins to the last moment of life. This effec* 


i 







72 


HUMAN PHYSIOLOGY. 


The blood changed in the capillaries from red to dark. 

probably extends no further than the smaller veins; but the heart, 
by its active dilatation, draws the blood from them into the larger 
veins. And as these two forces, at the two ends of the venous 
system, are at work up to the last moment, the whole of this 
system is filled with blood. 

110. The fact, that the larger arteries are commonly found 
nearly empty of blood after death, gave the ancients the idea 
that air circulated in arteries, while blood circulated in veins. 
Hence, the name, artery, is derived from two Greek words, sig¬ 
nifying to hold air. And hence, also, by long established cus¬ 
tom, in common language, the blood is spoken of as running in 
our veins; and it would sound strangely, if, in common, and 
especially in poetical language, we should speak of it as running 
in our arteries also. Although there were from time to time 
some glimpses of the true idea of the circulation, it was not 
really developed and demonstrated till about two hundred 
and thirty years ago. Harvey spent eight years in maturing 
his ideas on the subject. When he published them, they en¬ 
countered much opposition; but he lived long enough to see 
them almost universally received by the medical world, although 
the profession was in a much less enlightened state than it is at 
the present day. 

111. I will now take you a atep farther in the development 
of the plan of the circulation. I have said that the office of 
the arteries is to conduct the blood to the network of capil¬ 
laries, and that in the capillaries the blood has reached its 
place of destination where it is to be used. The formative ves¬ 
sels, appended to the capillaries, take from the blood what they 
need for their various purposes, and at the same time there is 
added to the blood refuse matter from the waste of the tissues. 
The blood, then, is changed while it is in the capillaries. You 
see the change in its color. In the arteries it was red; but, 
after passing through the capillaries, it appears in the veins of 
a purple color. It is also as much changed in other properties. 
It is no longer fitted to nourish the body. It would even prove 
a poison to any organ if it should flow into its capillaries. If it 
should, for example, be sent to the brain, instead of bright ar¬ 
terial blood, that organ would cease to do its office; insensibility 
would ensue, and life would soon be destroyed, if the flow of 
red blood could not be established. 

112. This purple blood, which comes back to the heart from 
the capillaries by the veins, must, therefore, be in some wav 
changed to red blood, before it is again sent all over the system 





THE CIRCULATION. 


73 


Change in the blood in the lungs. Course of the circulation. 


through the arteries. This change is effected in the lungs. As 
the purple blood returns to the heart, it is sent by the heart to 
the lungs, in order to be exposed to the air before it is sent 
again over the system. For'this purpose there are two circula¬ 
tions, and the heart is a double organ; or rather, there are in 
effect two hearts for the two circulations, for the two sides of 
the heart have no communication with each other. The appa¬ 
ratus for all this is very complicated, but I think it can be made 
clear to you. 

113. I present, first, a diagram, which is intended to repre¬ 
sent merely the course of the circulation, without regard to 
proportionate size, or to minutiae in the arrangement of the ap¬ 
paratus. Let a represent the right side of the heart, c the left 
side, b the lungs, and d the general system of the body. The 
arrows show the direction in which the blood flows. In all the 
shaded part the blood is venous or purple, and in the part not 
shaded it is arterial or red. We will now take some point of 
beginning, and trace on the Figure the course of the circulation. 


FIG. 25. 



DIAGRAM SHOWING THE COURSE OF THE CIRCULATION. 

We will start at a, the right side of the heart. The blood re¬ 
ceived here, of a purple color, from the whole body by the 
veins, is sent by the heart to b , the lungs. Here it changes to 
red blood, and passes by veins back to the heart—but, observe, 
it is to the left side of the heart, c. It is now sent by this left 
half of the heart to all parts of the system, represented by d. 
Here, in the capillaries, it is changed to purple blood, and goes 
back by veins to the right side of the heart, a , the place where 
we started. 


7 





74 


HUMAN PHYSIOLOGY. 


Two circulations and two hearts. Arrangement of valves. 


114. You see, then, that there are two separate circulations, 
one through the general system, and the other through the lungs 
alone. In both circulations the blood is sent from the heart 
by arteries, and is brought back to it by veins. But notice that, 
while in the general circulation the red blood is in the arteries, 
and the purple in the veins, in the circulation through the lungs 
it is reversed—the red blood is in the veins, and the purple is 
in the arteries. So, also, while the change of the blood in the 
capillaries of the general system is from red to purple, in the 
capillaries of the lungs it is from purple to red. 

115. There are not only two sides or halves of the heart, 
separated entirely from each other, but each of these sides has 
two apartments, with valves or folding doors between them, so 
arranged that the blood can pass one way through them, but 
not the other. There are also valves at the beginning of the 
great artery of the heart, the aorta. These are so arranged 
that the blood can go freely out of the heart into the artery, 
but not a drop can get back from the artery into the heart. 
There are similar valves, also, at the beginning of the great ar¬ 
tery, by which the purple blood is sent from the heart to the 
lungs. 

116. In Fig. 26, is represented a section of the right side of 
the heart, for the purpose of giving you an idea of the arrange¬ 
ment and the relative size of the two apartments. The auricle , 
a, so called because a part of it has some resemblance to 
an ear, receives the blood from the whole system by two 
large veins, b, b , called the venae cavae. 

From the auricle it passes into the ven- fig. 26 . 

tricle , v , which by its contractions sends a 

it to the lungs through the pulmonary 
artery, f. The valve between the au¬ 
ricle and ventricle is composed of three 
membraneous sheets, which are held at 
their edges by small tendinous cords, d , 
just as a sail is held by the ropes at its 
corners. This valve permits the blood 
to pass from the auricle into the ventri¬ 
cle ; but when it attempts to pass back 
from the ventricle to the auricle, it section of the right 
pushes back the sheets of the valve, they SIDE 0F THE heart. 
being prevented from going too far back 
by the tendinous cords. There are also valves at e, the beginning 
of the pulmonary artery, which allow the blood to pass through 









THE CIRCULATION. 


75 


Relation between the auricles and the ventricles. 


them into the artery, but no blood can pass through them from 
the artery back into the ventricle. I shall soon call your atten¬ 
tion again to these different valves, that you may see more par¬ 
ticularly their structure and arrangement. 

117. The auricle and ventricle act in this way in propelling 
the blood. When the auricle contracts, the ventricle dilates * 
to receive the blood from the auricle. The valves between them 
are open while this is taking place. But the next moment the 
ventricle contracts and the auricle dilates. You at once see, 
that if now the valves between them should be open, the blood 
would be forced back into the auricle. But the membranous 
sheets of these valves shut upon each other as the ventricle 
contracts, and thus prevent the blood from going back. It 
therefore is discharged through the pulmonary artery, /, the 
valves there being open. And when the ventricle dilates, you 
can see that the blood would, from suction, enter it from the 
artery as well as from the auricle, if the valves at the orifice of 
the artery should remain open. They are accordingly shut 
when the ventricle dilates. You see, then, that when the 
auricle dilates and the ventricle contracts, the valves between 
the auricle and ventricle are closed, and the valves at the mouth 
of the pulmonary artery are open; and, on the other hand, 
when the ventricle dilates and the auricle contracts, the valves 
between them are open, and the valves of the pulmonary artery 
are closed. 

118. Dr. Carpenter has a very good illustration of the rela¬ 
tion of the actions of the auricle and ventricle, in a representa¬ 
tion given in Fig. 27. The apparatus which is represented 
consists of two pumps, a and 6, the pistons of which move up 
and down alternately. These are connected with a pipe, c, /, 
in which there are two valves, d and e, opening in the direction 
of the arrows. The portion c of the pipe represents the venous 
trunk discharging its blood into the heart, and the portion f 
the artery which is the outlet for the blood. The pump, a, 
represents the auricle, and the pump, 6, the ventricle. When 
the piston in a is raised, the fluid enters through c to fill it by 
suction, as it is termed. When, now, its piston is lowered, tho 
fluid is forced through the valve d into the pump b , (which re¬ 
presents the ventricle,) whose piston is at the same time raised 
to receive it. And when the piston in b is lowered in its turn, 

* This dilatntion is an active one, ns was stated in § 106 , when speaking of the heart 
as a whole. The ventricle does not dilate because the blood is forced into it, but the 
blood rushes into it because it dilates. 






76 


HUMAN PHYSIOLOGY 


Ventricles larger and stronger than the auricles. Valves of the aorta. 


( 


FIG. 27. 



the fluid being prevented from returning into a, by the closure 
of the valve d, is forced through the valve e into /, representing 
the discharging tube, the artery. At the same time, a fresh 
supply of fluid is received into a by the raising of its piston. 

119. I have described the auricle and ventricle of one side 
of the heart, the right side. The left side is constructed very 
much in the same way. You will observe, in Fig. 26, that the 
ventricle is much more capacious than the auricle. The auricle 
is indeed the antechamber to the ventricle. The ventricle, 
too, you see, is much thicker in its walls. It is made very 
strong, because it does by far the principal part of the work. 
I remark here, in passing, that the size of the whole heart is 
about that of the closed hand of the individual. 

120. I will now call your attention to a more particular view 
of the valves of the heart. We will take, first, the valves 
which are at the beginning of the aorta, the great artery of the 
body, going out from the left ventricle. These are very much 
like the valves of the veins seen in Fig. 23. There are three 
of them. They are like little pockets arranged around the ori¬ 
fice of the artery, and looking toward the tube of the artery. 
Of course, w’hen the ventricle contracts, and forces the blood 
into the artery, these pockets are pressed by the blood flat 
against the sides of the artery. But when the ventricle dilates, 
and the blood attempts to go back from the artery into the 
ventricle, it gets into these pockets, and bulges them out toward 
the heart, and thus the mouth of the artery is closed. But you 
can see that if these pocket-like valves had plain curved edges, 
they would not effect a perfect closure. There would be a 



















THE CIRCULATION. 


77 


Peculiar provision in the valves of the aorta. 


little space in the very middle of the orifice of the artery which 
would be left open. This is made plain by Fig. 28, which pre¬ 
sents the orifice of the artery with 
its closed valves, as it would appear 
seen from the interior of the heart, 
if the three valves had plain curved 
edges. There would be a space left 
between them. But this difficulty is 
remedied by a very simple contriv¬ 
ance. A little fleshy projection is 
placed upon the middle point of the 
edge of each valve, of such a size 
that the three projections together 
just fill the space A. When, there¬ 
fore, the valves are closed, no blood 
can go back from the artery into the 
ventricle. This arrangement is shown in Fig. 29, in which the 
aorta, a, is laid open and spread out, so as to show the three 
valves with their projections on the edges. At b and c, are the 
openings of the two arteries that supply the walls of the heart 

FIG. 29. 


VALVES OF THE AORTA. 

with blood for their growth and repair, for the heart is con¬ 
structed and repaired from its own blood. The valves at the 
orifice of the pulmonary artery are arranged in the same man¬ 
ner as those which are at the orifice of the aorta. 

121. The valves which are between the auricles and the 
7* 



FIG. 28. 








78 


HUMAN PHYSIOLOGY. 


Arrangement of the valves between the auricles and ventricles. 

ventricles I have already partially described. They are folds 
of strong white membrane, their edges being held by numerous 
small tendinous cords. And these cords are manned, as we may 
express it, by muscles attached to the walls of the heart. The 
office of these muscles is to hold on to the cords that are fast¬ 
ened to the edges of the valves, and prevent these sheets of 
membrane from flapping back too far when the powerful ven¬ 
tricle contracts. It is by a nice adjustment of forces that these 
valves act with such exactness. They are of greater extent 
than the valves which are at the mouth of the aorta and the 
pulmonary artery, and, therefore, it would not do to leave them 
to act alone, as those valves do, upon simple mechanical princi¬ 
ples. The living muscular fibre must be introduced as the 
agent to control and regulate these principles in their applica¬ 
tion here. If it were not done, the consequence would be, that 
when the ventricle contracts with prodigious force, as it some¬ 
times does when the circulation is in a great state of excitement, 
the light tendinous fastenings would be ruptured by the pres¬ 
sure of the blood upon the valves. As it is now, the strong 
but yielding muscular bundles, to which these tendons are 
attached, regulate with great exactness the closing of the valves. 
Even if there were no need of any regulation, by muscular 
action, of the movement of these valves—if the tendons would, 
in all cases, let the valves go back to just the right point—as 
they are not extensible, and have no elasticity, it is manifest 
that there would be more danger of rupture than there is with 
the present arrangement. The tendons cannot be stretched, and, 
therefore, under great pressure they might break. In Fig. 30 
is a representation of a portion of this valvular apparatus. The 
engraving was made from a drawing of the part taken from 
the heart, and pinned upon a board for the purpose. At m, 
you see the sheet of membrane; o, o, are two of the muscles 
attached to the inside of the ventricle, to hold on to the ten¬ 
dons, h , that are fastened to the edge of the membrane. This 
membrane is now in the position that it is when the valves are 
open, that is, lying in a line with the little tendons and their 
muscles. But when the ventricle contracts, the blood, pushing 
against the membrane m, carries up the free edge to which the 
tendons are fastened, which, meeting the free edges of the other 
valves, closes with them the communication between the auricle 
and ventricle. 

122. In looking at Fig. 26, you observe that, while there are 
valves between the auricle and ventricle, and at the mouth of 




THE CIRCULATION. 


79 


No valves at the openings of the ven® cav®. Why this. 


FIG. 30. 



PART OF THE VALVULAR APPARATUS BETWEEN THE AURICLE 
AND THE VENTRICLE. 

the artery going out from the ventricle, there are none at the 
openings of the two vence cavce , the veins that pour their con¬ 
tents into the auricle. Why is this ? Why is there no need 
of valves here to prevent a regurgitation into these veins when 
the auricle contracts ? It is because that, as the auricle con¬ 
tracts, there is at the same time the dilatation of the strong 
ventricle, making, of course, a suction in that direction so 
powerful as to counteract most fully any tendency to regurgita¬ 
tion into the veins. You readily see, that if the arrangement 
were reversed, and the auricle were stronger than the ventricle, 
then, when the auricle contracted, there would be regurgitation 
into the venae cavae, if there were no valves there to prevent it. 
The same remarks could be made in regard to the pulmonary 
veins, that pour their contents into the left auricle. 

123. Having thus examined the heart in detail, you are now 
prepared to look at it as a whole. For this purpose, I present 
to you, in Fig. 31, a front view of the heart, in which a is the 
right auricle , receiving the purple blood from the whole body 
by the two large veins, h and i, called the vence cavce ; b is the 
right ventricle , that receives the blood from the right auricle, 
and sends it to the lungs by the pulmonary artery , f; c is the 
left auricle , which receives the red blood from the lungs, by 
the pulmonary veins, g, g, g; d is the left ventricle that re¬ 
ceives the blood from the left auricle, and sends it all over the 
body through the aorta, e. You observe, that you see but a 
part of the left auricle and ventricle, they lying partly behind 
'he right ventricle. You do not see the very beginning of the 






so 


HUMAN PHYSIOLOGY. 


General view of all the parts of the heart. 


FIG. 31. 



FRONT VIEW OF TIIE HEART. 


aorta, for, as it rises from the left ventricle it is at first con¬ 
cealed behind the top of the right ventricle and the beginning 
of the pulmonary artery. It then forms an arch, from which 
it sends forth branches to the head and upper extremities; and 
it afterwards passes down behind the heart, to supply with its 
branches the trunk of the body and the lower extremities. In 
the line of division between the two ventricles, b and d, you 
see one of the coronary arteries, as they are called, which, 
coming from the beginning of tha aorta, as described in § 120, 
supply the walls of the heart with blood. 

124. To make you quite familiar with the relations of the 
different parts of this complicated organ, and with the course 
of the blood through its different apartments, I give vou, in 







THE CIRCULATION. 


81 


Course of the blood through the different cavities of the heart. 


Fig. 32, a map of the heart, with the names placed upon the 
parts. I will describe the circulation with this map before you. 
The dark blood is received from all parts of the body by the 
vence cavte —from the parts above by the descending cava, and 


FIG. 32. 



Irom the parts below by the ascending cava. These veins pour 
the blood into the right auricle. From this it passes into the 
right ventricle, which sends it by the pulmonary artery to the 
lungs. From the lungs it returns by the pulmonary veins to 
the left auricle. It then passes into the left ventricle, from 
which it is sent by the aorta to all parts of the body. 

125. In Fig. 33 is represented the heart, situated between 
the two lungs, with the arteries which carry blood from it, and 















S2 


HUMAN PHYSIOLOGY. 


Situation and connections of the heart. Its harmonious action. 

the veins which pour their blood into it. The lungs are repre¬ 
sented as being drawn apart to the right and left in front, so 
as to expose fully the heart and its vessels. The sac containing 
the heart, and the packing cellular tissue are removed, so as to 
lay the heart and its vessels bare. At a is the trachea or wind¬ 
pipe ; on either side of it are the two arteries, the carotids, 
which go to the head; c is the artery which goes to the arm; 
b t b , are the jugular veins coming from the head, d, d, the veins 

FIG. 33. 


b a b 



LUNGS, HEART, AND PRINCIPAL BLOOD-VESSELS. 


from the arms, all empting their contents, as you see, into the 
descending cava; e is the right auricle, receiving the blood 
from the two cavse; / the ascending cava; g the right ventri¬ 
cle, i the left ventricle, and h the descending aorta. 

126. I have been thus particular, and have led you through 
some repetitions in the description of some of the figures, "in 
order that you may get a clear idea of the complicated mecha¬ 
nism of the circulation. And now, perhaps, you will inquire, 
in what way all these four apartments of the heart contract 
and dilate, so as to have the organ act as one harmonious 
whole. You have seen how the auricle and ventricle of one 






THE CIRCULATION. 


83 


The causes of the two sounds of the heart. Its forward impulse. 

side act in relation to each other—the auricle contracts when 
the ventricle dilates, and the ventricle contracts when the auri¬ 
cle dilates. Now, the harmony of action between the two sides 
is preserved by having the two auricles act together, and 
the two ventricles act together. And this action produces 
two sounds, which may be heard by applying the ear to the 
chest of any one on the left side. The first sound is rather 
a prolonged and heavy one, the second is light and quick. 
They are very well represented by the syllables lub-tup. The 
first sound occurs when the strong action of the heart is per¬ 
formed, that is, when the ventricles contract. It is owing 
to several causes. One of these is the impulse of the heart 
against the walls of the chest; the cause of which I shall 
speak of soon. Another is the flapping together of the 
valves between the auricles and the ventricles, to prevent the 
blood from regurgitating into the auricles, when the ventricles 
contract to force out their contents. The light and quick 
second sound is caused principally by the flapping together of 
the valves at the mouths of the aorta and the pulmonary 
artery when the ventricles dilate. The pulse (which I have 
already remarked upon in § 100) is produced by the impulse 
given to the blood by the contraction of the ventricles. There 
is, therefore, a pulse in the arteries of the circulation through 
the lungs, as well. as in those of the circulation through the 
general system. Wherever there is an artery there is pulsation. 

‘127. The impulse of the heart against the front wall of the 
chest on the left side is easily explained. The heart is so en¬ 
veloped by the lungs, that only a small portion of it comes 
near to the front wall of the chest, and such is the situation of 
the heart, that this portion comes to the left of the middle line 
of the chest. The position of the heart is an oblique one, its 
upper part being both farther back and more to the right than 
its lower part. Keeping in view this position of the heart, you 
will readily see how the impulse is produced against the front 
of the chest at its lower part. The aorta, in going from the 
heart, makes an arch upward and backward, to go down in 
front of the spine; and it is the tendency to straighten out, 
produced in this arch by the force of the blood thrown into it 
by the ventricle, that causes the throwing of the heart forward 
by a spring. This is easily seen as illustrated by Fig. 34, in 
which a is the spinal column ; 6, the front wall of the chest; 
d, the heart; and c, the arch of the aorta. When the heart 
throws the blood into this arched tube it tends to straighten it; 




84 


HUMAN PHYSIOLOGY. 


Arrangement of the sac of the heart. Its lubrication. 


but, as the aorta is fastened to the 
fixed spine behind, there can be no 
impression made in that direction. FIG - 34 - 

The straightening of the arch must 
therefore occur in the other direction, 
to the front; and therefore the heart 
is thrown a little forward, as represent¬ 
ed by the dotted lines. The change 
of position thus produced is indeed 
but slight, but it is sufficient to cause 
the impulse. The entrance of the 
blood into the pulmonary artery per¬ 
haps aids in the result, but not very 
materially. 

128. The heart, as I have already 
hinted, is inclosed in a sac, called the 
pericardium, which, at its upper part, 

is fastened all around the vessels that proceed from the heart. 
This sac is lined on the inside by a serous membrane, which also 
lines the outside of the heart, being reflected over upon it from 
the pericardium. This membrane forms, therefore, a sac without 
any outlet. This is made plain by Fig. 35. In this diagram, 
showing the plan of the serous membrane of the pericardium, 
a, a are the auricles \ v,v, the ventricles; 6, c, the vessels pro¬ 
ceeding from the heart; p the serous membrane lining the out¬ 
side of the heart; p\ the same membrane reflected from the 



FIG. 35. 



PLAN OF THE PERICARDIUM. 










CIRCULATION. 


85 


Action of the heart involuntary. Number of its beats. 

upper part of the heart on to the inside of the pericardium. 
The arrangement of this membrane, as it fits on to the heart, 
is much like the common double nightcap, as it fits on to 
i the head; and if it were . dissected off* whole from the outside 
of the heart and the inside of the pericardium, it would be 
like such a nightcap when taken off from the head—that is, a 
sac without an outlet. Now, this sac is kept moistened by a 
fluid exuding from its whole surface, so that, as that part of it 
which lines the outside of the heart, in the motions of that 
organ, rubs against that part which lines the pericardium, the 
lubrication prevents any injury from the friction. This lubri¬ 
cating fluid is continually renewed, the exhalents and the absorb¬ 
ents balancing each other in their action. When the exhalents 
secrete more fluid than the absorbents can take up, it accumu¬ 
lates, making what is called dropsy of the heart. 

129. The heart, as you have seen, is a complex arrangement 
of muscles. And these muscles are wholly involuntary; that 
is, they are not at all under the direct control of the will. No 
one can by an exercise of the will make his heart beat slower 
or faster. As I shall show you in another chapter, this organ 
is kept at work by its nervous connection with the spinal mar¬ 
row. It has no repose, as the voluntary muscles have, unless 
you call the intervals between the contractions and dilatations 
of its several parts intervals of repose. The amount of work 
which it does is enormous, if we calculate it for a lifetime. 
The heart of an adult beats, that is, each one of the four cham¬ 
bers of this organ dilates and contracts, about 70 times in 
a minute. This would make 100,800 times in 24 hours, 
36,792,000 times in a year, and 2,575,440,000 times in a life 
of 70 years. In children, the action of the heart is much more 
rapid, and in disease it sometimes reaches in them to 160 or 
even 200 beats in a minute. It is thus that this organ, situ¬ 
ated in the centre of the complicated apparatus of the circula¬ 
tion, labors continually, by night and by day, in keeping the 
blood in motion. The two circulations of the general system 
and of the lungs are ever going on. The blood is ever moving 
in all the cavities of the heart, in every artery, and vein, and 
capillary. It never stops till it is arrested by death. 


8 




86 


HUMAN PHYSIOLOGY. 


Apparatus of respiration. Air-cells in the lungs. Their size. 


CHAPTER VII. 

RESPIRATION. 

130. You saw, in the last chapter, that the purple venous 
blood is sent to the lungs to be changed into arterial blood. 
The great object of the apparatus of respiration is to introduce 
the air to the blood, so that it may act upon it, and produce 
this change. Another object is effected at the same time, viz., 
the production of the voice, by the striking of the air upon 
the vocal chords in the larynx, as it is forced out from the 
lungs. This will be made the subject of a future chapter, and 
I propose now to show how the chief object of respiration, 
which is so immediately essential to the continuance of life, is 
secured. 

131. The lungs are spongy bodies, filling up a large part of 
the chest, and surrounding the heart. They are in common 
language, the lights; and you can see what they are in man 
by observing the lights of other animals. They are composed 
chiefly of air-tubes, air-cells, blood-vessels, and nerves, packed 
together with the common packing material of the body, cellu¬ 
lar membrane. The spongy lightness of the lungs is owing to 
the air-cells or vesicles. You can get some idea of the propor¬ 
tion of these cells to the solid part of the organs if you 
inflate the lungs of some animal, as the sheep or calf, by blow¬ 
ing into the windpipe. These cells are exceedingly minute. 
It is in them that the change is effected in the blood. The 
capillaries holding the blood branch out on the walls of the 
cells, and the blood is acted upon by the air through the pores 
of the vessels. The object, therefore, of respiration is to in¬ 
troduce the air freely into these cells. The air enters through 
the windpipe, and this branches out into tubes called bronchi, 
which divide and subdivide, till they become very minute, and 
then end in the air-cells. These cells are estimated to be about 
the Toirfh. °f an inch in diameter. Some calculations have 
been made in regard to the extent of surface which they would 
all make if they could be spread out in one sheet. There is of 
course no great accuracy in such calculations; but we can readily 
see that the aggregate surface must be immense, and, therefore, 
the blood is thus very extensively exposed to the action of the 




RESPIRATION. 


87 


Air-tubes. Relative situation of the lungs and the heart. 

air. In Fig. 36 is represented tlie lung of one side, d; the 
branches of the bronchi of the other lung, c, at the lower part 
of which, e, they are represented as they branch out minutely 
to open into the air-cells; b is the trachea or windpipe, and a 


FIG. 36. 


a 



LUNGS AND AIR-TUBES. 


is the larynx at the top of it. It is through a chink called the 
' glottis, in the larynx, that all the air passes as it goes into and 
cut from the lungs. This will be particularly described here¬ 
after. 

132. In Fig. 33, in the last chapter, you see represented the 
relative situation of the heart and lungs, the lungs being some¬ 
what separated, however, from the heart, to the right and left, 
in order to show that organ fully. In their natural position 
they are close to the heart, and cover up all of it, except a 
small portion in front and to the left side, where its beating is 
so plainly felt. Both the heart and the lungs are suspended in 
the chest to the upper part of the walls of this cavity, and are 
fastened also to the spinal column in the rear. The large vessels 
of the heart, and the bronchi of the lungs, serve as the princi- 








88 


HUMAN PHYSIOLOGY. 


Pleura. Mechanism of breathing. Provision for expansion of the chest. 


pal means of suspending these organs, as you can readily sea 
by the Figure. The lungs are covered by a white, shining 
membrane, which also lines the inside of the walls of the ches- 
(§ 67.) called the pleura. This is always kept lubricated by 
a watery fluid, so that, as the lungs expand and the chest 
moves, the friction will be attended with no inconvenience or 
injury. You may perhaps ask why, as the lungs follow the 
walls of the chest in its expansion, they could not have been 
fastened to these walls throughout their whole surface. The 
principal reason probably is that, if this were the arrangement, 
the intimate vascular connection, which would in this case 
exist between the walls of the chest and the lungs, would ex¬ 
pose the delicate texture of these organs more frequently to 
injury from external violence. As it is now, the effusion, or the 
inflammation, consequent upon a blow on the chest, is not 
apt to affect the lung in the neighborhood, because it has 
no direct connection with it by nerves and blood-vessels. 

133. You are now prepared to see by what mechanism the 
air is alternately introduced to and expelled from the lungs. The 
chest incloses a large space, which can be made much greater by 
certain movements of its walls. It is this expansion of the cav¬ 
ity of the chest, effected by certain muscles, which, by creating a 
vacuum, causes the air to rush into the chest through the tra¬ 
chea, just as air rushes into the bellows when the space within 
is expanded by the separation of its walls. That you may un- 
derstand_ how the expansion of the chest is effected, I now 
proceed to describe the chest. In Fig. 37 you see the frame¬ 
work of the chest. At b, 6, is the spinal column, the grand 
pillar supporting the walls of this cavity. The ribs, c , c, go 
from this with a large curve round to the breastbone, a, in 
front. The ribs, however, do not join directly with the breast¬ 
bone, but there are cartilages intervening, as you observe in 
the Figure. The collar-bone goes from this breastbone across 
to the top of the shoulder. The ribs are twelve on each 
side. The lowest two are attached only to the spine, and are 
called floating ribs. The whole is so constructed as to allow a 
very considerable expansion of the cavity. As, in effecting this 
expansion, the ribs are carried upward and forward with the 
breastbone, the ends of the ribs at the spine move but very 
slightly. As the chest is kept in constant motion, lightness in 
its walls is an object of some importance ; and, at the same 
time, it is necessary that the structure should be a strong one, 
in order to guard effectually the lungs from injury. Both' of 




RESPIRATION. 


89 


Framework of the chest. Bones. Cartilages. Muscles. 



FIG. 37. 


these objects are secured, by having the walls in front and at 
the side composed of so many bones, well bound together by 
the muscles which move them. If these bones were all in one, 
it would be necessary that it should be quite thick, to answer 
as a defence, and then it would be a heavy and unwieldy thing 
to move. The cartilages which connect the ribs to the breast¬ 
bone are a great safeguard. They give elasticity to the struc¬ 
ture as a whole, and the ribs are not very liable to be broken, 
because of the yielding of the cartilages with which they are 
connected. 

134. This framework is filled out with connecting material, 
chiefly muscles, which effect the expansion of the chest in in¬ 
spiration. First, there is a large expanse of muscle and tendon 
stretching across the lower part of the chest, separating its con¬ 
tents from the contents of the abdomen below. The edge of this 
muscle, which is called the diaphragm , is fastened to the spine 
behind, to the end of the breastbone before, and all around the 
lower ribs. It is arched upward; and against its concave sur¬ 
face press upward the liver and stomach, while the lungs and 

8 * 






90 


HUMAN PHYSIOLOGY. 


Diaphragm. Its action in inspiration and expiration. 

the heart press downward against its convex surface. The dia¬ 
phragm is represented in Fig. 38. The ribs are cut away in 
front, so as to give a front view of the cavity of the chest, C, c, 
the lungs and heart being entirely removed. D D is the 
diaphragm, very high in the central portion, which is tendin¬ 
ous, but descending very low at its edges at the sides and in 
the rear. 


FIG. 38. 



DIAPHRAGM. 
Front View. 


135. You can see that, if all the muscular fibres in the dia¬ 
phragm contract, the arch will be flattened, and thus the room 
in the chest will be enlarged. To occupy this new room thus 
made, the air rushes in through the windpipe. This is inspira¬ 
tion. In expiration , the reverse movement takes place—the 
arch of the diaphragm rises, and, compressing the lungs, forces 
the air out of them through the trachea. In inspiration, as 
the diaphragm is flattened, it pushes down before it the 
stomach, liver, <fec., and hence the pressing out of the abdomen, 
which is so sensibly felt, if the hand be placed upon it during 
the act of inspiration. In expiration, on the other hand, the 




RESPIRATION. 


91 


In expiration little muscular action. Elasticity the chief agent. 

abdomen retreats inward. These two opposite states of the 
arch of the diaphragm, and of the walls of the abdomen, are 
represented in Fig. 39. It is a side view, the libs being cut 
away. C c is the cavity of the chest, and C a, the cavity of 
the abdomen. The diaphragm and the abdomen are represented 

FIG. 39. 



DIAPHRAGM. 
Side View. 


as they are in expiration. The dotted line marks the flattening 
of the arch of the diaphragm, and the projection of the al>- 
domen, as they occur in inspiration. It is supposed that in 
ordinary expiration, there is little, if any, muscular action— 
that, as the diaphragm, which in inspiration pushed down the 
stomach and liver, and thus thrust out the walls of the ab¬ 
domen, ceases to contract and relaxes, the mere elasticity of 
the parts below, and especially of the abdominal walls, restores 
the former condition of things, and so the diaphragm is car¬ 
ried upward, and expiration results. When, however, the ex- 










92 


HUMAN PHYSIOLOGY. 


Other muscles, besides the diaphragm,-act in inspiration. 

piration is at all forcible, it is produced in part by the action 
of the muscles of the abdomen and some of the muscles about 
the chest. 

136. While this dome-shaped muscle, the diaphragm, is the 
principal agent by which the chest is enlarged, there are other 
muscles which do the same thing in another way. In Fig. 40, 
a is the spine; c, c, c, the ribs ; b , the breastbone; <f, the col¬ 
lar-bone ; g, the diaphragm. You observe, on the right side 


FIG. 40. 


i a c 



WALLS OF THE CHEST. 

of the chest, certain muscles, i, extending from the spinal 
column in the neck to the first rib. When these contract, the 
effect will be to raise this first rib, and all the others, being 
attached to it, of course follow. And, as the ribs, as you see 
in Fig. 37, slant downwards from the spine toward the front, 
the result will be, that all the ribs will be carried together for¬ 
ward and upward. This result is the more effectually secured 
by muscles which pass from rib to rib, as seen at e, e, c, e. In 
this Figure, the ribs, c, c, c, are left bare on the left side, to show 





RESPIRATION. 


93 


Arrangement of muscles between the ribs. 


the arch of the diaphragm, g , the dotted line indicating it on 
the right side. 

137. There are two layers of muscles connecting the ribs, 
the fibres of which cross each other, as represented at M, in 
Fig. 41. R R are parts of two ribs. The spaces between the 


FIG. 41. 



ribs are filled with muscular fibres, arranged as represented in 
in the Figure. If the fibres were straight, as at L, they could 
not bring the ribs as near together as the oblique fibres do. 
For, as muscles can not shorten themselves, at the farthest, more 
than one-third of their length, the straight fibres could bring 
the ribs only one-third nearer together, while it is obvious that 
the oblique fibres, with the same contraction, can do much 
more than that. These muscles between the ribs not only, 
then, help to raise all the ribs as a body, as mentioned in § 136, 
but they bring each rib nearer to the one above it. This in¬ 
creases the expansion of the chest, especially as the ribs are so 
joined to the spine, that if a rib be moved upward, it must be 
carried outward as well as forward. You can see, then, that 
by the operation of these muscles in the neck and between the 
ribs, the diameter of the chest will be increased from front to 
rear, and also from side to side. 

138. The chest is expanded, then, in two ways—by flatten¬ 
ing the arch of the diaphragm, and by raising the ribs. In 
ordinary quiet respiration, this expansion is effected chiefly by 
the diaphragm. But when there is a call for 'more active 
respiration, as in violent exercise, the muscles which raise the 
ribs act strongly, and hence the heaving of the chest, as it is 
called. Their action is violent when from disease, as in asthma 
for example, it is difficult to introduce sufficient air into the 
lungs. 

139. The lungs, heart, &c., accurately fill the chest in all the 
variations of size to which its cavity is subjected in respiration. 









94 


HUMAN PHYSIOLOGY. 


Change in the blood effected in the air-cells. 


For, when the chest is expanded, the spongy lungs swell out to 
follow its walls, and the air rushes in through the trachea to 
fill the expanding air-cells. If, now, there were an opening 
through the walls of the chest, communicating with the out¬ 
side of the lung, when the chest expanded, the air would rush 
in at this opening as well as through the trachea, and the lung 
would be compressed in proportion to the freeness of the open¬ 
ing. This has sometimes occurred from disease and from 
wounds. If a free opening were made at the same time in 
both sides, both lungs would be compressed, and death would 
be produced by suffocation, as really as if some obstruction in 
the windpipe pr*rented the air from entering the lungs. 

140. I ha vp said that the change in the blood, from purple 
to red, is effected in the air-cells. The blood and the air are 
brought very near together for this purpose; and yet they are 
kept entirely separate, except when, from disease, the blood 
escapes into the air-cells and air-passages, and is then expecto¬ 
rated mingled with air. It is supposed that the air in the cells 
acts upon the blood through the pores of the vessels containing 
it, which branch out on the walls of the cells; for if dark 
venous blood be inclosed in a bladder, the air will act through 
the pores of the bladder, and gradually change the outer por¬ 
tion of the blood to a red color. 

141. These air-vesicles, then, do an important work. The 
change which is effected in them is immediately essential to the 
continuance of health, and even of life. If the air be in any way 
shut out from them death occurs at once. And so important 
is it that they should do their work well, that extraordinary 
provisions are made to secure an abundance of room for them 
under all circumstances. For the cavity of the chest, as you 
have seen in this chapter, can be expanded to a very great ex¬ 
tent. It would indeed be difficult to conceive how a greater 
range of expansion could be secuY*d. As the air-cells are 
called upon to do more work at some times than at others, 
there are special provisions for a larger dilatation of the chest 
than is required m ordinary quiet respiration. Thus when, 
from violent exercise, the blood is coursing rapidly through the 
lungs, and more air is therefore needed to change it to red 
arterial blood, the chest is largely expanded by calling into 
action muscles, which do but little, if any thing, in ordinary 
breathing. 

142. As the apparatus of respiration is so especially ar¬ 
ranged to secure room for the lungs under all circumstances. 




RESPIRATION. 


95 


Injury done to the air-cells by compression of the chest. 

it must be very deleterious to the health of the body to inter¬ 
fere with this arrangement. If the expansion of the chest in 
breathing be limited by any pressure, every air-cell must be 
embarrassed in doing its part in changing the blood. Either 
all of them must be unduly contracted, or some of them must 
become obliterated, so that there will not be as many vesicles 
as there should be. In either case, the organ is disabled in 
proportion to the amount of the compression. The blood is 
not as good as it would be if there were enough vesicles, and 
they could perform their work without constraint. The vigor 
of the system is therefore lessened. And, besides, the lungs 
themselves are especially liable to disease from this unnatural 
confinement. 

143. Much injury is undoubtedly done to the lungs that are 
thus confined, when any strong exercise is taken. If the chest 
be left free to expand to its fullest extent when occasion re¬ 
quires, this injury^is avoided. For when the strongly and 
rapidly contracting heart pumps the blood in such quantities 
into the lungs, the widely expanding chest draws in the due 
amount of air to change the extra amount of blood. All the 
air-vesicles are ready to do their duty, and, therefore, no violence 
is done to the delicate texture of the lungs. But if these or¬ 
gans be compressed, the dilatation of those vesicles that are not 
obliterated, in the midst of the commotion of the difficult res¬ 
piration, is very unequally effected, and some of them are 
stretched beyond their proper dimensions. At the same time, 
the blood must be here and there obstructed in its passage 
through the lungs, producing what is termed congestion. And 
if this violence be repeated from time to time, permanent dis¬ 
ease will after a while be the result. 

144. From the considerations in the two last paragraphs it 
is manifest, that the interference with the due expansion of the 
lungs, which so commonly results from the modes of dress in 
the female sex, must be one of the prominent causes of con¬ 
sumption, to say nothing of other diseases arising from this 
cause. This interference is effected in two ways—chiefly by 
compression of the chest directly, but also by the pressure 
which the load of clothing hanging from the girt waist must 
make upon the upper part of the abdomen. This latter cause 
interferes with that forward movement of the abdomen which, 
as you saw in § 135, is necessary to the flattering of the arch 
of the diaphragm in the act of inspiration. The extent to 
which compression of the chest is sometimes carried is seen by 




96 


HUMAN PHYSIOLOGY. 


Change of the form and capacity of the chest by compression. 

comparing the two outlines in Fig. 42. One is an outline, of 
the Venus de Medicis, the universally recognized beau ideal 
of beauty of form in the female, and the other is an outline 

FIG. 42. 



of the form of a lady with an artificially small waist. In Fig. 
43 is represented the framework of the chest of its natural 
size, and as it is sometimes contracted by fashion. The Figures 


FIG. 43. 



representing the contraction of the chest may appear at the 
present time as caricatures, for a very small waist is not con¬ 
sidered now to be as essential to beauty in the female form, as 
it was twenty-five years ago. The truth, as uttered by medical 
men, has had some effect. But the evil is remedied only in 








RESPIRATION. 


97 


Cause of death in drowning. Singular provision in the whale. 


part. The chest of the female is still too much begirt, in obe¬ 
dience to the tyranny of fashion, to allow of the free expan¬ 
sion, to secure which such special pains are taken by nature. 
The evil begins in childhood. The chest is moulded during 
its growth to the shape which fashion prescribes. It could not 
be done after the chest has attained its full size. The torture 
of the compression necessary to do it could not be endured. 
In childhood, therefore, while the boy’s chest is left to grow 
in its natural shape and dimensions, the girl is begirt so tightly 
as to embarrass her respiration, because nature is too ungen- 
teelly large in her patterns to suit her case. The subject is 
an important one ; but as this book is not designed to treat of 
hygiene, I can not go into it further. 

145. It is the interruption of the change which is effected 
by the air upon the blood in the lungs, that produces death in 
drowning. The very common supposition, that considerable 
water gets into the lungs in drowning, is erroneous. Very 
little water ordinarily gets in—not enough to occasion any em¬ 
barrassment. The difficulty is, that the air is kept out, and 
not that the water gets in. The drowning person makes at¬ 
tempts to inspire, but the moment that the water reaches the 
epiglottis, the door of the windpipe, it causes at once, by its 
irritation, a spasmodic closure of the epiglottis, so that almost 
no water is introduced. In the mean time, the purple blood 
continues to be thrown by the right ventricle of the heart into 
the lungs. But the little air contained there soon parts with 
its oxygen; and then the change in the blood ceases to occur, 
and dark blood is sent from the lungs to the heart, and thence 
to all the organs. These can not go on to do their duty with¬ 
out the stimulus of arterial blood. The brain, therefore, gives 
out, and there is insensibility. The muscles cease to act, and 
all motion is gone. If a good supply of arterial blood could 
be furnished to all the organs until breathing could be again 
commenced, life would be preserved. And there is provision 
for such a supply in certain animals that can remain under 
water for some time. For example, in the whale there are 
large reservoirs for containing arterial blood, which can be used 
for the supply of the organs while he remains under water. 
When the supply begins to be exhausted, the animal of course 
has those uncomfortable sensations which a predominance of 
purple blood is so apt to produce. He manifests his uneasiness 
by his puffing and blowing, as he rises to the surface, to get a 
fresh supply of air, and with it a fresh supply of arterial blood 
in the reservoirs. 9 




98 


HUMAN PHYSIOLOGY. 


Respiration in fishes. Arrangement of the gills. 


FIG. 44. 


146. The apparatus of respiration varies in different animals. 
It appears in three forms—lungs, gills, and tracheae or air- 
tubes. The gills of the fish are arranged in fringed laminae, in 
order to present by all its minute divisions a large surface ; and 
these delicate organs are covered with a lid to protect them 
from injury. The blood-vessels which contain the blood to be 
changed branch out on the surface of the fringes of the lami¬ 
nae, just as the blood-vessels in lungs branch out on the surface 
of the air-vesicles. The air which is to change it is mingled 
with the water. It acts upon the blood, as the 
water containing it, after being taken into the 
mouth, of the fish, passes out through these la¬ 
minae, as through a sieve. That the air in the 
water is the cause of the change can be proved 
by experiment. If a fish be placed in a vessel 
with its orifice closed, so that no air can enter, it 
will soon die from suffocation, because the air in 
so small a portion of water is soon used up. 

Although the fish can not with his gills use air 
that is not mingled with water, it is supposed 
that it is merely because the gills soon become 
dry when exposed to the air, and that the air 
would act on the blood in the gills if they were 
only kept moist. Indeed, in the land crab, that 
has the power of living for some time out of the 
water, it has been found that there is a gland in 
the gill-chamber which furnishes a secretion to 
keep the gills moist. Gills differ much in their 
shape and arrangement in the various aquatic 
animals. In Fig. 44 is represented the arenicola 
or lob-worm. Here, the gills are in the form of 
tufts arranged along the outside of the body. 

They take a somewhat similar form in the larvse 
of many aquatic insects, as seen in Fig. 45. A 
large surface is presented to the air contained in 
the water by the delicate and beautifully arbor¬ 
escent gills of these animals. In insects, we find 
the respiration effected by trachece or air-tubes. 

These go into all parts of the body, and the air 
contained in them acts upon the blood in the ves¬ 
sels which branch out upon their walls. The in¬ 
sect, therefore, has no distinct respiratory organs 
situated in any one part of the body, but the 


lob-worm. 





RESPIRATION. 


99 


Respiration in insects. Tracheae. Stigmata. 


air is carried into every part. This seems to 
be necessary on account of the feeble circula¬ 
tion in the insect. The tracheae which, as 
Cuvier says, conduct the air in search of the 
blood, as the blood has no means of travelling 
in search of air, open on the surface by stig¬ 
mata, as they are called, which are of various 
shapes and number in different insects. In 
the grasshopper there are twenty-four, ar¬ 
ranged in four rows. You can kill an insect 
by suffocation by simply covering the stigmata 
with varnish. In Fig. 46 are represented the 
tracheae in an insect, the nepa or water-scor¬ 
pion. The tracheae, as you see, send branches 
out in every direction, so that air is introduced 

FIG 46. 


1st fair of 

LEGS. 

CHEST. 


WING CUT OFF..1 

2d PAIR OF 


I IG 45. 


TRACHEAE 


STIGMATA 


LARVA OF THE 
MAY-FLY" 



AIR-SACS. 


RESPIRATORY APPARATUS OF THE WATER-SCORPION. 

















100 


HUMAN PHYSIOLOGY. 


Respiration in birds. Apparatus for it extensive. 


into every part of the body. There are lungs, so to speak, 
everywhere in the insect. 

147. The apparatus of respiration is largely developed in 
birds for two objects—to provide for the extensive change in 
the blood which is required by. their great activity, and to give 
lightness to the body. To secure these objects there are air- 
sacs connected with the lungs, and located in different parts of 
the body; and in birds that fly rapidly and are long upon the 
wing, these sacs are very extensive, and even many of the 
bones are made hollow, and are connected with the air sacs. 
By this arrangement, the air is introduced extensively to the 
bjood in the capillaries on the walls of these sacs, and at the 
same time the body is made very light. And the heat gener¬ 
ated by the effort of flying must expand the air in the air-sacs 
and swell them out, and thus make the body lighter. In Fig. 47 
is seen this arrangement of air-sacs in the ostrich. The lungs, 
/, £, are quite small, but the air-sacs, c, c, c, are very large. 
The orifices by which they communicate with the lungs you see 


FIG. 47. 
t 



LUNGS OF THE OSTRICH. 







RESPIRATION. 


101 


Changes produced in the air in the lungs. 

in the Figure. In birds of great powers of flight, the air-sacs 
are much more extensive. This arrangement of air-sacs in 
different parts of the body of the bird bears some analogy to the 
tracheae distributed in the bodies of insects. 

148. You have seen that the object of the apparatus of re¬ 
spiration is to change venous blood into arterial, and you have 
also seen how the air is introduced to the blood in order to 
effect this change. And now the interesting inquiry arises, 
what are the actual changes which occur, both in the blood 
and in the air, in the lungs. If you take a tumbler filled 
with lime-water, and breathe into it through a tube, the lime- 
water will become turbid, and will soon deposit a sediment. 
This is chalk, or carbonate of lime, formed by the union of 
the carbonic acid gas exhaled from the lungs with the lime 
in the lime-water. Whence comes this carbonic acid gas, 
and how is it formed ? In order to answer this question satis¬ 
factorily, we must look at the chemical constitution of the air 
which we breathe. It is composed of two gases, oxygen and 
nitrogen. In every 100 parts of common air, there are 79 
parts of nitrogen and 21 of oxygen. It is found that the 
oxygen is that constituent of the air which is necessarv to 
life. If an animal be placed in a closed jar filled with com¬ 
mon air, he will soon die, and the oxygen will be found to have 
disappeared, while the nitrogen remains very nearly the same 
in amount. If, now, you place an animal in a jar of nitrogen, 
and another in a jar of oxygen, the one in the nitrogen will die 
immediately, while the other will be very lively until the oxy¬ 
gen is mostly used up by his lungs. The animal in the pure 
oxygen will breathe at first more rapidly than the animal in 
the jar of common air; and it is thought that oxygen is too 
stimulating for the lungs, and therefore needs to be diluted 
with the nitrogen, as it is in the air that we breathe. 

149. In the case of both the animal in the jar of air, and 
that in the jar of oxygen, carbonic acid is found to have taken 
the place of the oxygen which has disappeared. This gas is 
made by a union of oxygen with carbon or charcoal. It was 
formerly supposed that this union is effected in the lungs— 
that carbon is thrown off from the venous blood in the lungs, 
and that the oxygen of the air there unites with it, and so car¬ 
bonic acid appears in the air expired from the chest. But it has 
been discovered that the exchange is made in a different man¬ 
ner. It is not made in the lungs. The oxygen is absorbed by 
the blood, and goes with it to the heart to be sent all over the 





102 


HUMAN PHYSIOLOGY. 


Changes produced in the blood by the air. 

system. And it is in the capillaries that the oxygen unites 
with carbon to form carbonic acid. The union takes place 
while the blood is chanfrinff from arterial to venous, and is an 
essential part of the change. The carbonic acid thus formed 
in the capillaries, is brought back to the heart in the venous 
blood, and is discharged from the system in the lungs. That 
the change takes place as stated has been abundantly proved 
in various ways. It has been found by experiments which I 
will not detail, that carbonic acid exists in considerable amount 
in venous blood; while, on the other hand, there is much oxy¬ 
gen in arterial blood. The plain inference from this is, that 
oxygen unites with the blood as it passes through the lungs, 
goes with it to the capillaries, and there unites with the carbon, 
giving us the carbonic acid which we find in the blood in the 
veins, after it has passed into them from the capillaries. It has 
been found, also, that if frogs or other cold-blooded animals 
be placed in hydrogen or nitrogen, (gases which produce no in¬ 
jurious effect on them,) they will give off for some time nearly 
as much carbonic acid as they would have done in common 
air. In this case, as no oxygen is introduced into the lungs, 
the carbonic acid can not come from any union effected in 
these organs between carbon and oxygen, but it must be dis¬ 
charged by exhalation from the blood as it is passing through 
the lungs. Of course the discharge of the carbonic acid ceases 
after a little time; for, there being no new supply of oxygen by 
way of the lungs, as there is when the animal is breathing com¬ 
mon air, there can be no new formation of carbonic acid. But 
even cold-blooded animals can not live in these gases for any 
great length of time, although they are not positively deleterious 
to them, for oxygen is needed for the continuance of their func¬ 
tions. And in the warm-blooded animals, a constant supply 
of it is necessary—they will die if cut off from this supply 
even for a short time. 

150. The change which takes place in the blood, as it passes 
through the lungs, occurs to some extent when the blood is ex¬ 
posed to the air in any way. Thus, if blood be drawn from a 
vein into a bowl, the surface of it becomes red by the action 
of the air upon it. Carbonic acid is discharged from it, and 
the oxygen of the air takes its place, uniting with the bicod, 
just as the process occurs in the lungs. A larger part of the 
blood will be thus changed, if it be shaken so as* to expose 
more of it to the air. The change takes place to some extent 
even if a membrane be interposed between, as when the blood 




RESPIRATION. 


103 

Quantity of carbonic acid given out by the lungs. Necessity ol ventilation. 

is inclosed in a bladder. The oxygen of the air, in this 
case, is introduced through the minute pores of the bladder 
and the carbonic acid gas escapes through them. Precisely in 
this way is the change effected in the lungs, as already stated 
in § 140. The blood is separated from the air by being con¬ 
fined in blood-vessels, and the air in the vesicles acts upon it 
through the minute pores of these vessels. And, as the blood is 
divided into innumerable little streams, every part of it is acted 
upon by the air in the vesicles. Though the texture of the 
lungs is exceedingly delicate, and the separation between the 
air and the blood is almost as nothing, yet the blood is confined 
to its limits, even though it courses through these organs with 
great rapidity, and it never mingles with the air except as 9 
consequence of actual disease. 

151. The quantity of carbonic acid gas discharged from the 
lungs in the course of twenty-four hours is very great. Many 
experiments have been tried and calculations made to ascertain 
its amount, and I am within bounds when I state, that there is 
at least three-quarters of a pound of charcoal in the carbonic 
acid thrown off from the lungs of a common-sized adult in the 
course of twenty-four hours. This gas is a deadly poison. 
When accumulated in a considerable amount, as when char¬ 
coal is burned in an open furnace in a close room, it may prove 
immediately destructive to life. And in the very prevalent 
neglect of ventilation, the frequent accumulation of this gas 
from the respiration must prove more or less injurious to the 
health. Whenever the proper amount of oxygen gas is with¬ 
held from the lungs, and carbonic acid takes its place, the 
quality of the blood is impaired from incompleteness in the 
change effected in the lungs, and the vigor of the body must 
in this way be lessened, to say nothing of the deleterious influ¬ 
ence of this gas upon the nervous system. Though the results 
are not immediate and palpable, great injury is continually 
done to the health, of multitudes by the accumulation of this 
gas, in small close apartments, and in crowded assemblies. A 
congregation of twelve hundred people in two hours throw off 
from their lungs an amount of carbonic acid that contains 
seventy-five pounds of charcoal. And yet little pains is com¬ 
monly taken to carry off this vast quantity of poisonous gas, 
and replace it with pure air. 

152. As so much oxygen is absorbed in the lungs of all ani¬ 
mals, and so much carbonic acid is thrown out from them, the 
inquiry arises how the air is replenished with oxygen, and is 








104 


HUMAN- PHYSIOLOGY. 


Carbonic acid exhaled from the lungs of animals absorbed by plants. 


cleared of tlie carbonic acid which is thus so largely mixed with 
it. It is found that this is done, to a great extent at least, by the 
leaves of plants. The process which goes on in these lungs, as 
they may be called, of the plants, is quite the reverse of that 
which is going on in the lungs of animals. The carbon of the car¬ 
bonic acid which is thrown off from the lungs of animals is ab¬ 
sorbed by the leaves of plants, and the leaves replenish the air 
with the oxygen, which is so constantly and abundantly ab¬ 
sorbed in the lungs of the animal creation. Thus, the animal 
and vegetable kingdoms are sources of supply to each other. 
But it may be thought that there would be apt to be a surplus 
of oxygen in the atmosphere in warm climates, where the vege¬ 
tation is so luxuriant; while, on the other hand, there would 
be an accumulation of carbonic acid gas in the colder regions. 
This would be so, if the air were not so movable that the equi¬ 
librium is readily secured in either case. 

153. It is an interesting fact, that the presence of light is 
necessary to the process which I have described as going on in 
the leaves of plants. Each leaf may be considered as a labor¬ 
atory, and the light as the chief agent in effecting the chemical 
changes that occur in it. And it is found that no artificial 
light can do the work. It is only the light of the sun that is 
competent to this chemistry. And as these innumerable labor¬ 
atories are everywhere at work, absorbing the carbon and ex¬ 
haling the oxygen, to purify the air rendered noxious by the 
laboratories of the animal creation, we must confess it to be a 
mystery as to how the chemistry of the lungs of animals, and that 
of the leaves of plants should be kept so nicely balanced. The 
balance is so strictly maintained, that the chemical composition 
of the air is always found to be almost exactly the same. 

154. The heat of the body is maintained by the union 
which takes place in the capillaries between the carbon and 
hydrogen of the system, and the oxygen which is introduced 
into the blood through the lungs. It is a process analogous to 
combustion. When carbon or charcoal is burned in a ves¬ 
sel containing air, the oxygen disappears, for it unites with 
the carbon, and carbonic acid gas, therefore, appears in its 
place. The same union occurs in this case between carbon and 
oxygen, as we find occuring in the capillaries. A sort of com¬ 
bustion, then, is going on in every part of our bodies. And, as 
heat is evolved in the one case, so it is in the other. The same 
can be said of the burning of hydrogen and oxygen together. 
Heat is caused by the union thus produced between them, and 





RESPIRATION. 


105 


Animal heat. Produced by a sort of combustion. Three sources of fuel. 

so it is when they unite in the body. The water which is ex¬ 
haled from the lungs conies from this union of oxygen and 
hydrogen. It was formerly supposed that the union between 
the oxygen and the carbon and hydrogen takes place in the 
lungs, and that the heat is made there, and then is distributed 
over the whole system. But it was objected to this supposi¬ 
tion, that it made the lungs a sort of furnace for the rest of the 
body, and that, if the supposition were correct, there ought to 
be a much higher degree of heat in these organs than any¬ 
where else, which is not the case. Ingenious theories were 
broached to get over this difficulty; but it was at length dis¬ 
covered that the union between the oxygen and the carbon and 
hydrogen occurs in the capillaries of the body, instead of the 
lungs, and that the combustion, therefore, that produces the 
heat is everywhere, instead of being in one locality. 

155. The fuel for this combustion comes from three sources. 
One of these is the waste of the tissues. This furnishes a con¬ 
siderable amount of the carbon and hydrogen for the union 
with the oxygen, in all animals that are subjected, from their 
activity, to much wear and tear of the system. I barely al¬ 
lude to this now, and shall enlarge upon it soon. Another 
source of the fuel for combustion is food. The oily, sugary, 
and starchy kinds of food are devoted in a great measure to 
this particular purpose. These furnish a sort of floating fuel, 
as we may express it, which is carried about in the blood. 
Hence, we see, that our diet must necessarily be varied accord¬ 
ing to the weather and the climate. In cold weather, the heat 
of the body is more rapidly abstracted than in warm weather, 
and, therefore, we need then more of that food which affords a 
su pply of carbon a$d hydrogen. And so as to climate. The 
enormous quantity of oily food often consumed by inhabitants 
of very cold climates is used up by being burned, as we may 
say, in the capillaries to keep up the animal heat. Of course, 
keeping the body warm by fire and clothing relieves from the 
necessity of taking any large quantities of fuel-making food. 
Still, under the most favorable circumstances in this respect, 
there is a need of variation in diet to suit the weather and the 
climate, and we make this variation for the most part instinct¬ 
ively. Indeed there is a marked provision in nature for it. I 
will mention but a single example of this provision. While 
there is a large amount of fat in the bears and seals and whales 
which afford food for the Esquimaux and Greenlander, there is 
very little in the animals which furnish a part of the diet of th</ 





106 


HUMAN PHYSIOLOGY". 


Animal heat differs in cold and warm-blooded animals. Why. 

inhabitants of tropical climates. Another source, still, of ani 
mal heat is the store of fat which is laid up in the body. One 
design of this accumulation of fat in different parts of the 
body seems to be to provide for the heat when other sources 
fail. Thus, when disease destroys the appetite, and thus cuts 
off the supply of food, the fat wastes away, or rather is burned 
up, to keep up the temperature of the body. The fat is the 
great means of maintaining the requisite temperature when hi¬ 
bernating animals become torpid for the winter. They become 
very fat in the autumn, before crawling into their winter quar¬ 
ters, and in the spring they come out very lean, their fat having 
been consumed in keeping up the low degree of temperature re¬ 
quired during this time. 

156. As the amount of heat produced, when charcoal is 
burned in air, or when oxygen and hydrogen are burned 
together, depends upon the quantities of carbon and hydrogen 
that unite with the oxygen, so, also, the degree of animal heat 
depends upon the quantities of carbon and hydrogen that unite 
with the oxygen in the capillaries. This may be illustrated by 
referring to the effects of exercise on the heat of the body. 
When the circulation is quickened by exercise, the blood passes 
more rapidly than usual through the lungs, the respiration is 
consequently quickened, more air is introduced into the lungs, 
and therefore oxygen is more rapidly absorbed by the blood. 
At the same time, the action of the muscles effects a waste in 
their structure by the wear and tear, so that more carbon and 
hydrogen are ready to be released to be united with the in¬ 
creased oxygen. Hence comes the heat produced by exercise. 
So, too, those animals which are the most active, ordinarily 
have the most animal heat, and have the most extensive respi¬ 
ratory apparatus, so that there may be a free supply of absorbed 
oxygen to unite with the carbon and hydrogen of the changing 
tissues. It is in birds and insects that this union takes place 
most largely, and in them, therefore, the respiratory apparatus 
is very largely developed. This is to be attributed to their mus¬ 
cular activity, which produces so much waste matter that must 
be removed from the system. Cold-blooded animals, on the 
other hand, are very inactive. There is not, therefore, much 
wear and tear of the tissues. There is comparatively little 
waste, therefore, to be thrown off. And so but little oxygen 
needs to be introduced into the lungs, and consequently little 
heat is generated. To realize fully the contrast between the 
warm and the cold-blooded animals in these respects, observe, 




RESPIRATION. 


107 


Uniformity of animal heat in the warm-blooded. Interesting experiments. 

the representative of the one class, a canary bird, and a frog an 
the representative of the other. The frog is generally quiet, 
and only now and then takes a leap or croaks; but the bird 
is ever in restless motion, and sings much of the time with 
all bis might. The bird is warm with the heat generated by 
the constant union of oxygen with carbon and hydrogen in its 
capillaries ; but the frog is nearly as cold as the water in which 
he is immersed. The bird breathes rapidly, to let the oxygen 
of the air largely into his lungs ; but the frog scarcely seems 
to breathe at all, so scanty is the supply of oxygen which he 
needs. 

157. Cold-blooded animals are very nearly of the same tem¬ 
perature with the substances that are around them ; but warm 
blooded animals have a certain degree of temperature, which 
they maintain with considerable uniformity under all variations 
of temperature in the atmosphere. This in man is about ninety- 
eight degrees of Fahrenheit. This, you observe, is above the 
temperature of the surrounding air, except in exceedingly hot 
weather. The human body is therefore always giving off heat. 
Indeed it is essential to comfort that it should part with con¬ 
siderable heat, for any near approach of the atmosphere to 
ninety-eight degrees produces an uncomfortable sensation of 
heat. But the amount of heat which the human body can 
bear for a short time is much greater than the facts above 
alluded to would lead us to suppose. It was long taken for 
granted, that it could not safely bear, even for a short time, 
a heat much higher than that which is endured in hot climates. 
The truth on this subject was at length discovered by accident. 
Two Frenchmen were employed by government, in 1760, to 
devise some method of destroying an insect which infested the 
grain at that time. The result of their experiments was the 
discovery, that by subjecting the grain to a certain degree of 
heat in an oven the insect was destroyed, and the grain not 
injured. While they were trying their experiments, a girl 
offered to go into the oven and mark the height of the mer¬ 
cury in the thermometer. It stood at 260° ; and, after remain¬ 
ing there for ten minutes, which she found that she could do 
without any great inconvenience, she marked it at 288°, that 
is, 76° above the boiling point of water. These facts led to the 
famous experiments of Dr. Fordyce and Sir Charles Blagden, 
in England. With wooden shoes, tied on with list, they went 
into a room in which the thermometer showed the air to be 
at 260°. Their watch chains were sc hot that they could scar cely 




108 


HUMAN PHYSIOLOGY. 


Different degrees of torpor in hybernnting animals. 

touch them, and eggs were roasted hard in twenty minutes, and 
beefsteak was cooked in thirty-three minutes. And yet the 
same air that produced these results was breathed by them with 
impunity, and it raised the heat of the body but very little. 
The air which was breathed out from the lungs was so much 
cooler than the air of the room, that it was refreshingly cool to 
the nostrils, and to the fingers as they bio wed upon them. In 
such cases, the evil effects of the heat are prevented chiefly by 
the great amount of perspiration that occurs, the vaporization of 
this abstracting the heat, which would otherwise accumulate in 
the body and produce disastrous results. The exhalation from 
the lungs, also, has some influence. 

158. In the state of hibernation, to which I have several 
times referred, the torpidity varies in degree in different ani¬ 
mals. In cold-blooded animals, respiration and circulation may 
cease altogether in this state. In them the movements of • life 
are often, perhaps we may say generally, as fully suspended as 
they are in the seed that is kept from heat and moisture. They 
may be-preserved in this state for a long time and yet revive. 
Serpents and frogs have been kept in an ice-house for three 
years, and then have been revived on being brought out into a 
warm atmosphere. In the warm-blooded animals that hiber¬ 
nate the torpidity is less deep than in those which are cold 
blooded. In them the respiration and the circulation become 
very slow, but never entirely cease. Indeed some species take 
food with them into their winter quarters, and occasionally wake 
up sufficiently to eat. But most of them are in a quiet, deep 
sleep, from which they do not arouse at all till the winter is 
past. In 'this state, as life is nearly, sometimes quite at a stand, 
there is no wear and tear, and therefore no change in the tissues, 
and so there is no need of the introduction of oxygen by the 
respiration. Dr. M. Hall, in his experiments and observations, 
found that the bat, when completely torpid, consumed no oxy¬ 
gen, and discharged no carbonic acid from the lungs, although 
its circulation was not entirely suspended. 

159. The more active is the respiration of animals, the less 
able are they to bear a deprivation of air. A warm-blooded 
animal will die if it be under the water only a few minutes; 
but a cold-blooded animal can live under the water for some 
time, because it is not in so urgent need of oxygen. And, for 
the same reason, a warm-blooded animal, in a state of hiberna¬ 
tion, may be kept under water for a long time without destroy¬ 
ing life, although when in its active state it would die on being 




FORMATION AND REPAIR. 


109 


Formative vessels appended to the capillaries. 

kept under water for only a few minutes. And this suggests a 
probable explanation of those cases, in which individuals have 
been restored, after having been under the water longer than 
the usual time that suffices to destroy life in drowning. In such 
cases, the condition is not simply that of a drowned person. 
A blow, or the shock of body or mind, or both, may have in¬ 
duced a suspension of active vitality, like that which we see in 
the animal in a state of hybernation. The bare fact of immer¬ 
sion in the water may have but little or even nothing to do 
with the actual condition. Such a state of things is especially 
to be suspected in those cases in which the countenance does 
not exhibit the usual dark and full appearance of drowned per¬ 
sons. 

160. I have thus shown the extensive play which the respi¬ 
ration has in the vital operations of the system. I have shown 
what the chemical changes are, which it effects directly in the 
lungs, and indirectly in the system. And you have seen how 
the animal heat is produced by these changes, and how unac¬ 
countably it is so regulated, that it seldom varies to any ex¬ 
tent from its fixed standard. But it is to be remembered that, 
while the lungs, and even the capillaries, everywhere are thus 
chemical laboratories, the nervous system exerts a constant 
influence upon this chemistry of the body. This is especially 
seen in regard to the production of heat, but it is true of 
the whole range of the chemical operations. The laboratories 
would all cease their work if their nervous connections were 
destroyed. 


CHAPTER VIII. 

FORMATION AND REPAIR. 

161. The building and the repairing of the various struc¬ 
tures of the body are done by vessels appended to the capil¬ 
laries. The capillaries having received from the arteries the 
blood, the building material, the formative vessels select from 
it, while it is in these capillaries, whatever they need for their 
purposes. The selection is made according to the tissue or 
structure to be formed. Those vessels which, for example, form 
bone, select from the blood very different constituents from those 
which make nerve or muscle. 


10 





110 


HUMAN PHYSIOLOGY. 


Selecting power of the formative vessels. Their concert of action. 

162. It is wonderful that the blood can be formed from such 
a variety of food as is often taken into the stomach. But it is 
far more wonderful that from the blood can be made so many 
and such different structures. How different are the teeth from 
the gums which surround them ; and yet both are made from 
the blood. Observe, in some particular part of the bod} 7 , how 
many different structures there are which are all made from the 
same common material. Take, for example, those which are 
in and aroilnd the eye. There are, the skin of the eyelids; the 
eyelashes; the vascular lining on the inside of the lids; the 
cartilages of the lids; the firm, white coat of the eye, giving 
to the eyeball its firmness; the thin, transparent window in 
front, setting into the firm, white coat, like a watch-glass into 
the case; the beautiful iris, a round moving curtain with a cen¬ 
tral opening; the lens behind this opening; the optic nerve ex¬ 
panded on the inside of the cavity of the eye; the muscles 
that move the eye, with their tendons; the tear-gland; the 
cushion of fat on which the eye reposes; the bone which forms 
the socket, &c. All these various textures are formed from the 
blood ; and the different workmen are as unerring in their se¬ 
lections from this common material, as if they were intelligent 
beings. Indeed, no ordinary intelligence could accomplish such 
a selection. It is effected, inscrutably to us, under the direction 
of an all-wise Intelligence, and by Almighty power. 

163. But these builders of the body not only have the power 
of selecting their building materials from the blood, but they 
work in concert. Each company of builders work together in 
harmony, as if they were under intelligent leaders. And 
though different companies may be in close proximity, there is 
no disagreement nor interference. For example, the builders 
of a tooth and the builders of the gum around it, do not en¬ 
croach on each other; but each do their appropriate work with¬ 
in their assigned limits. Even when different structures are 
intermingled, as when tendon and muscle mingle together at 
their place of union, there is no confusion in the work of the 
two sets of laborers. In Fig. 48 you see the difference in struc¬ 
ture between the transparent cornea in the front part of the 
eye and the white coat, the sclerotic coat, into which the cornea 
is set like the crystal of a watch. It is represented as seen 
magnified 320 times. The dotted lines mark the place of 
union. The cornea, a, is a much more open structure, you ob¬ 
serve, than the sclerotic coat, b. The builders of these twc 
structures, though some of them are in such near neighborhood 






FORMATION AND REPAIR. 


Ill 


Concert of action shown in producing different shapes. 


FIG. 48. 



never encroach on each other, but each set adheres strictly to 
its own kind of work. The sclerotica-makers never go to mak¬ 
ing the open work which you see in the cornea. If they should 
do so at any point there would be a little transparent window 
at that point ip the white of the eye ; and if the cornea-makers 
should at any point make close work like that in the sclerotica, 
here would be a white spot in the cornea. 

164. The concert of action which we observe in the different 
sets of formative vessels is to be looked at in another point of 
view. It is such that they give a definite and peculiar shape to 
the structure which they make. Each bone differs in shape 
from every other bone, each muscle from every other muscle; 
and so of other parts. There is very great variety of shape in 
the structures of the body ; and each shape can be determined 
only by a certain concert among the builders. That you may 
realize in some measure the extent of this variety, observe 
again the numerous different textures which I have mentioned 
as making up the eye. Each of these has its own peculiar 
shape, and its definite limits. Its builders work after a fixed 
plan, and within fixed bounds. 

165. This concert of action may be looked at in still another 
point of view. If the different structures in the body were 
made, as a crystal is, by layer after layer of particles deposited 
upon the outside, wonderful as the concert among the little 
builders would be in that case, it would not be any thing like 
as wonderful as it is now. In the growth, that is the construc¬ 
tion of any part, the addition is made by the formative vessels at 
every point of the part, and not upon the outside merely. As 
these builders are at work enlarging the part in the growth 
frojn infancy to childhood, they must so act in concert, as to 






















112 


HUMAN PHYSIOLOGY. 


Change of action. The teeth. Tadpole and frog. 


preserve the same general form in the part during all the suc¬ 
cessive stages of growth. And, as all the different stiucturea 
of the body enlarge together, there must be agreement between 
different sets ; else there would be encroachment and confusion. 
Thus in the growth of the tiny arm of infancy to the sturdy 
arm of manhood, each set of builders must during all this time 
keep within its proper limits, so that there may be just the right 
proportion, and the right position of bone, and muscle, and 
tendon, and ligament, and cellular membrane, and skin, and 
nail, &c., that make up the arm. 

166. But this concert of action appears the most wonderful 
when a new action, or change of action is called for. In the 
transition from childhood to youth, for example, the builders 
of the apparatus of the voice, the larynx, all at once become 
unusually active in their work, and a great enlargement of this 
musical instrument, for such it is, takes place, so that it may 
now utter the grave notes of manhood. Soon, too, the beard- 
builders begin their new work upon the face. And during the 
period of childhood new operations have been con^nually* insti¬ 
tuted among the builders of the teeth, as one tooth after 
another has made its appearance, and as the new set have re¬ 
placed the old. To produce in the enlarging jaw a new set of 
teeth to take the place of the smaller and less numerous first 
set, and to bring them out in a symmetrical arrangement, re¬ 
quire a very complicated series of operations. To effect each 
one of these, there must be concert of action among the forma¬ 
tive vessels; and there must be a most wonderful concert 
among the different successive sets of builders, to make 
all these series of operations work out at length the general 
result. 

167. This change of action in the formative vessels is 
strikingly exemplified in some animals. I refer to those that 
so entirely change their forms during the period of their exist¬ 
ence. I will give two ex^nples. The first is the common 
frog. He is at first what is termed a tadpole, and goes throuo-h 
many successive changes to become a complete trog. These 
changes are represented in the following figures. The relative 
sizes are not preserved, the tadpole state being represented re¬ 
latively much too large, for the purpose of showing more 
clearly the development of the legs. The young tadpole is 
represented in Fig. 49. It has a large head and body, and a 
long flat tail by which it swims easily. There are no promi¬ 
nences to indicate the putting forth of any thing like limbs. It 




FORMATION AND REPAIR. 


113 


Change of action in the silk-worm. Concert preserved in these coses. 


FIG. 50. 



has gills, which are loose fringes on each side of the head. 
These gills after a time disappear, and it has another set of 
gills arranged under a fold of skin very much like the gills of a 
fish. The form is then as in Ficr. 50. The next change is 
this. The hind legs begin to grow out as seen in Fig. 51. 
Next, the fore legs appear as seen in Fig. 52. The tail is still 
very large. This now gradually disappears while the legs grow 
as represented in Fig. 53. In Fig. 54, representing the perfect 
frog, the tail has entirely disappeared. With these exterior 
changes interior ones have been going on also. The animal, 
which was at the first a real fish, breathing with gills 
and swimming in water, has lost its gills, and has now a pair 
of lungs ; and it is no longer able to remain long under water, 
without coming to the surface to breathe the air. 

168. The other example is the silk-worm. It is represented 
in Fig. 55. When it has attained its full growth, it passes into 
what is termed its chrysalis state, Fig. 56, it having previously 
woven for itself from its silken thread a case or cocoon. 
While it is in this state of inactivity great changes are going 
on in its structure, and it at length becomes a perfect winged 
insect, as represented in Fig. 57. 

In the two cases which I have described, in each successive 
change, the concert of action in the formative vessels is pre- 














114 


HUMAN PHYSIOLOGY. 


Change of action to meet new exigencies. 

served, but it is after a new plan. This change of plan makes 
the concert of action exceedingly wonderful. 

FIG. 55. FIG. 56. 



169. The change of action in the formative vessels, which is 
sometimes called for by accident and disease, exhibits in an in¬ 
teresting manner the concert between these vessels as in¬ 
fluenced by circumstances. When a bone is broken, these 
formative vessels set themselves to work to repair the injury, 
by forming new bone between and around the two ends of 
bone, which new bone we call callus. In this case, the bone- 
builders extend their range of operations to meet the new 
necessity ; and in doing so they maintain the same concert 
which marked their usual operations before the bone was 
broken. I stated in § 105, that when an artery is tied, to 
cure an aneurism, the circulation in the limb is kept up bv the 
small arteries that go off from it above the ligature, communi¬ 
cating with those that branch off below; and that, in order to 
make the circulation perfect, some of these communicatino* 
arteries gradually enlarge, to meet the necessities of the case 
Now, this enlargement is not a mere dilatation produced b' 
the distending blood. The arteries grow in thickness as wel. 
as in capacity. The artery-builders are awakened to a new ac- 
tivity, and make the arteries in this quarter after a larger pat¬ 
tern than the one originally designed for them. 

170. Concert of action under successive changes is strikingly 
exhibited in the processes of inflammation. The following ac¬ 
count of these processes is from a work published by the 
author, entitled “ Physician and Patient.” “ You see a swelling. 








FORMATION AND REPAIR. 


115 


Illustration from processes of inflammation. 

It after a while begins to soften. There is matter in it, bnt it 
is not yet very near the surface. But soon, at some point, it 
comes nearer and nearer to the surface, the wall of the abscess 
thus becoming constantly more thin, till, at length, it opens 
and discharges. The discharge continues till the swelling is 
nearly all gone, and the remainder is absorbed, and the part 
is restored to its natural state. Just look for a moment at 
the complicated character of this apparently simple operation. 
Here is quite a large deposition of substance which is to be re¬ 
moved ; and this is the object to be effected. Observe how it 
is done. The softening of the swelling is not a mere change 
of solid substance into a fluid, as if by decay, but it is the re¬ 
sult of an active process, which we call suppuration. When 
this process is properly performed good pus is made, or as 
the old writers in medicine rather quaintly expressed it, laud¬ 
able pus. This process of suppuration, when it is well done, 
does not go on here and there in the swelling, making it like a 
honeycomb with a multitude of little abscesses; but there is a 
consent, an agreement of action by the vessels of the part, as 
really as if they worked intelligently. It is this consent 
of action which not only makes the line of movement 
in the abscess, but points it towards the surface, instead of 
giving it some other direction, laterally or inward, upon some 
of the internal organs. But it is further to be observed, that 
in this agreement of action, the vessels of the part do not all do 
one thing. Three different offices are performed by them in 
the different quarters of the abscess. While some of these 
little workmen are forming the pus, there are others thinning 
the wall of the abscess in the direction of the surface, by 
absorbing or taking up the substance there; while there are 
others still, in the rear, and at the sides of the abscess, deposit¬ 
ing substance, in order to make a barrier to prevent the pus 
from being diffused in the surrounding parts. Each class of 
these workmen perform their particular work with even more 
exactness and harmony, than would be expected of any com¬ 
pany of intelligent laborers under the direction of a leader. 
The absorbents absorb together, the wall-builders build together, 
and the makers of pus make pus together, and deposit it in a 
common reservoir. 

171. But observe farther, and you will soon see an entire 
chano-e come over the whole scene of operations. When the 
absorbents have completed their passage for the pus through 
the skin, the pus is gradually discharged from its reservoir, and 





116 


HUMAN PHYSIOLOGY. 


Formative vessels and absorbents act in concert. 


the “ occupation ’’ of the pus-makers is soon “ gone.” The wall 
builders also cease their work, and while the vacancy becomes 
tilled up by contraction and deposition, the wall of defense, so 
carefully maintained so long as was needed, is now taken up 
by the absorbents, workmen which seem to know just when, as 
well as how, to do their duty.” 

172. Here you have concert of action exemplified in a 
complicated set of associated actions, to accomplish a tempo¬ 
rary purpose. These actions, as you see, change in the 
different stages of the process, each one being performed just at 
the time, and during the period that it is wanted. And when 
the temporary purpose aimed at is accomplished, the vessels of 
the part resume at once their ordinary duties. It is to be ob¬ 
served also, that the concert of action is not confined to the 
formative vessels; but it appears also in those vessels called 
absorbents, of which I shall speak soon more particularly. 
And these two sets of vessels do not interfere with each other, 
but have a sort of agreement together in accomplishing the 
general result. This concert of action is plainly seen among 
the absorbents, not only in this case, but in all the cases that I 
have cited as exhibiting it among the formative vessels. For 
example, in the case of the frog (§ 16V) while the formative 
vessels are constructing the legs, the absorbents are removing 
the tail. So in the case of the teeth (§ 166) while the 
formative vessels are constructing the second set, the absorbents 
remove the ends of the fangs of the teeth in the first set, so 
that they are loosened in their sockets, and are thus taken out 
of the way of the coming teeth. And indeed, wherever there 
is formation, there is absorption; and the same concert of 
action always appears. 

173. I have spoken of the great variety of structures, which 
are made out of the same material, the blood. Besides this, 
all the different secretions are also formed from the same 
material. This appears wonderful when we look at the differ¬ 
ence between such secretions as the tears, the ear-wax, the 
gastric juice, the bile, &c. And it appears more wonderful still, 
when we consider that these various glands, or factories, as we 
may call them, are built from the same material out of which 
they make their products. There is one curious exception to 
this. It is in the case of that large gland, the liver. This 
gland is built and kept in repair, like all the other glands, by 
arterial blood. But while they make their secretions out of 
this arterial blood, the liver makes its secretion out of venous 





FORMATION AN1) REPAIR. 


117 


Formation of all parts from the blood. Waste. Lymphatics. 

blood, which is brought to it for that purpose as described in 
§ 108. 

174. Thus, al) the solids and fluids in the body are made 
from the blood. Even the heart itself is made from the blood 
which it pumps out into the aorta; for from this aorta go out 
some small arteries, to carry blood to the walls of the heart for 
its growth and repair. These arteries are represented in 
Fig. 31. 

175. There is not only construction going on in every part 
of the system, but there is waste also. The wear and tear of 
the ever-moving machinery continually makes some of the par¬ 
ticles useless, and these must in some way be removed. I pro¬ 
pose now to show how this is done. 

176. There-are two kinds of waste particles; and for the dis¬ 
posal of them two different plans are pursued. Some of the 
waste particles, though wholly useless where they are, can be 
rendered fit to be used again by being subjected to certain pro¬ 
cesses. These, therefore, are not thrown out of the system, but 
are taken up by absorbents, and are carried where the neces¬ 
sary processes can be applied to them; and then they are in¬ 
troduced into the blood, to make again a part of the building 
material. But there are some waste particles that can not bo 
used again ; and these are so managed as to be got rid of at 
various outlets of the system. These two kinds of particles are 
taken up by two different sets of absorbents. The selecting 
power which they thus exert is as unerring as if they were pos¬ 
sessed of intelligence; and it is wholly unaccountable, although 
some physiologists have attempted to explain it. 

177. The particles which can be used again are taken up by 
absorbents, which are termed lymphatics. These vessels are 
much like the lacteals, the absorbents in the intestines. They 
unite together, as they come from all parts of the body, into 
two trunks. One of these is the thoracic duct (described in 
§91), which is the common duct, both of the lymphatics 
and the lacteals, (Fig. 17,) and in which the chyle and the 
lymph, as the fluid in the lymphatics is called, are mingled to¬ 
gether. The other trunk, which receives the lymph from but a 
small part of the body empties its contents into a large vein at 
the right side of the top of the chest. The largest part of the 
lymph, therefore, unites with the chyle, and is poured with it 
into the circulation, and the rest reaches the same destination 
by another way. It all becomes with the chyle a part of the 
blood. But before this is done it passes, like the chyle, through 




118 


HUMAN PHYSIOLOGY. 


Two kinds of waste particles. Excretion and secretion. 

glands, in order to fit it to become again a part of the building- 
material of the body. These glands are every where in the 
track of the lymphatics. They are often enlarged from disease, 
and then they can be readily felt. This is often the case with 
these glands in the neck. In relation to this appropriation of 
waste particles, which I have thus described, it may be truly 
said that man lives in part upon his own flesh. 

178. Those waste particles which are entirely useless are 
taken up by the veins directly into the circulation. They then 
travel the rounds with the blood, and are thrown off from the 
system by organs appropriated for that purpose. These organs 
are the lungs, the skin, the liver, the kidneys, &c. Each of 
these excretory organs is fitted to throw off its particular part 
of the waste. Thus the lungs, excrete a kind different from 
that which the skin does; and so of the rest. The lungs, as 
you saw in the chapter on respiration, throw off in the form of 
carbonic acid gas, large quantities of the carbon evolved in the 
wear and tear of the system. The liver, the skin, &c. throw 
off parts of the waste which differ from that which is thrown 
off by the lungs. Why it is that the waste matter is thus in¬ 
troduced into the circulation to be carried to the excretory or¬ 
gans, instead of having special channels appropriated to the 
particular office of carrying it to its outlets, we know not. And 
how it can thus be mixed with the blood, and be carried about 
the system without proving noxious, is a mystery. That it can¬ 
not be long retained in the blood without doing injury, is shown 
by the evil results, which come from a suspension of excretion 
from any of the organs that I have mentioned. 

179. It is interesting to observe that some of the excretory 
organs perform other functions besides that of mere excretion.* 
Thus the lungs, while they excrete carbon, absorb oxygen, 
without which life could not go on. At the same time, too, 
they act as the bellows for the organ of the voice, the larynx, 
as you will see in the chapter on that subject. So also, the 
liver, while it excretes what would be noxious if it remained in 
the blood, puts its excretion into such a form, that it proves, as 
you saw in the chapter on digestion, an auxiliary in some of 
the processes of the digestive organs. 


* The words excretion and secretion , are often applied to the same thing. Excretion, 
strictly speaking, should be applied only to something to be thrown off , and not to some¬ 
thing formed to be used. But sometimes an excretion is so formed, that it can be used, 
and then the word secretion is also applicable to it. Thus the bile, while it is an ex¬ 
cretion containing noxious particles to be thrown off from the system, is put to use 
and so it is as often called a secretion as an excretion. 








FORMATION AND REPAIR. 


119 


The skin. Cuticle. True skin. Papillae. 



180 . The skin, while it is an extensive excreting organ, per 
forms other important offices. It serves as a firm yet very 
flexible and soft covering to the body, protecting its internal 
parts from injury. It is highly endowed with nerves for two pur¬ 
poses—the one, that it may act as a sentinel to warn of danger; 
and the other, that it maybe the seat of the sense of touch. 
That you may see how well it is fitted FIG> 58> 

to perform these various functions, 

I will describe here its structure. 

What is very commonly spoken of as 
the skin, is not really the skiu, but 
only a covering for it. When the 
skin is rubbed off", as it is expressed, 
it is only this covering of the skin, or 
cuticle, which is removed. The skin 
which is raised by a blister is this cu¬ 
ticle. The great object of the cuticle 
is to protect the true skin, which is 
very highly endowed with nerves for 
the purposes mentioned above, and 
which therefore, if uncovered, would 
prove a source of severe suffering. As 
it is, the cuticle protects the skin effec¬ 
tually, and yet does not interfere with 
its functions as the organ of the sense 
of touch. It is of so slight and so 
soft a texture, that the nerves of touch 
may readily receive impressions 
through it. It is composed, as you 
will see in the next chapter, of many 
layers of minute round cells, the 
outermost layers being made up of 
these cells broken, and emptied of the 
fluid which they contained. The 
true skin, which the cuticle covers, is 
of a fibrous texture, with a good 
supply of both nerves and blood ves¬ 
sels. On the surface of this true skin 
next to the cuticle are eminences called 
papillae. In these are seated the ex¬ 
tremities of the nerves of touch. 

Fig. 58 represents a highly magni- Vertical section of the 

fled section of a bit of the skin from sole of the foot. 












120 


HUMAN PHYSIOLOGY. 


Tubing in the skin. Insensible perspiration. Sebaceous glands. 


the sole of the foot; a is the cuticle; c is the true skin; b re¬ 
presents the papillae. You observe that the deepest layers of 
•the cuticle, next to these papillae, are more colored than the 
outer ones. The coloring matter of the skin is situated here. 
You observe also a tube which runs up through the cutis or 
■true skin and the cuticle, and in the latter part of its course 
has a sort of cork-screw arrangement. This is the discharging 
tube of the sweat-gland, d , lying within the true skin, and sur¬ 
rounded with globules of fat. These glands are more numer¬ 
ous in some parts of the skin than in others. They are par¬ 
ticularly numerous on the palms of the hands, and on the soles 
of the feet. Mr. E. Wilson counted, with the aid of the mi¬ 
croscope, 3528 of them in a square inch on the palm of the 
hand. Reckoning the length of one of these at one quarter of 
an inch it gives 882 inches or 73£ feet of tubing in this small 
•space. He calculated the amount of this tubing in the skin of 
the whole body as being 48,600 yards, or nearly 28 miles. 
‘The amount of excretion from the seven millions of these tubes, 
which open on the surface of the skin, is very great. Many 
•experiments have been tried to determine what the amount 
is in 24 hours, but approximations only to the truth, of course, 
•could be obtained, and the results of the experiments have 
•differed much. While the excretion is great in amount, it is 
very important. It is, as you have seen in the chapter on 
Respiration, a great means of regulating the temperature of 
4he body. It is also the means of discharging from the body 
a portion of its waste. This waste is dissolved in or mingled 
with the water or vapor of the perspiration. The perspira¬ 
tion is ordinarily insensible , as it is termed ; that is, it is in the 
form of vapor. But sometimes, as in vigorous exercise, when 
the sweat glands are rendered very active, chiefly to prevent too 
great an accumulation of heat, the perspiration becomes sensible. 

181. There is another set of glands in the skin called 
-sebaceous glands, which secrete an oily fluid. They have 
also thin tubes like the sweat glands. They are most 
abundant where the skin specially needs an oily lubrica¬ 
tion, as where there are folds in the skin or hairs, or 
where the skin is exposed to friction, or to the drying atmos¬ 
phere. They are very abundant on the face and head. The 
amount of the oily secretion of these glands is very great in 
the skin of races fitted to inhabit warm climates. Every hair 
has sebaceous glands connected with it, as represented in 
Eig. 59 ; in which b is the hair emerging from the skin; 




FORMATION AND REPAIR. 


121 


Influence of labor on wear and tear, and on absorption. 


FIG. 59. 



C 

HAIR 

and sebaceous glands. 


a a are the sebaceous glands pouring their 
secretion by thin tubes into the tube or 
canal in which the hair grows ; c the root 
of the hair surrounded with fat globules. 

From all this you see that the skin, with 
its two sets of glands and tubes, its nerv¬ 
ous papillae, and its layers of constantly 
renewed cells, making the cuticle, is a 
complicated orgau, and is thus fitted to 
perform its functions as an organ of sen¬ 
sation, and at the same time of excretion, 
while it is also a pliable but firm cover¬ 
ing for the body. 

182. You have seen in the facts de¬ 
veloped in this chapter, that there is con¬ 
stant change going on in all parts of the 
body. Particles which have become use¬ 
less are taken up by the absorbents, while 
the formative vessels deposit others to take 
their places. The rapidity with which 
this change occurs, depends mostly upon 
the activity of the individual. The busy 
laborer, whether the labor be bodily or mental, requires more 
nourishment than the indolent man, because there is more 
waste in his case, from the wear and tear occasioned by motion 
or thought, and there is therefore a necessity for a larger sup¬ 
ply of repairing material. The difference, it is true, is not as 
great in regard to mental labor, as in regard to that of the 
body ; but still it is very apparent. This dependence of the 
amount of change in the system upon the degree of activity is 
very manifest, if we compare different animals together in this 
respect. I have already contrasted the frog and the canary 
bird in regard to respiration (§ 156,) and they can be con¬ 
trasted in this respect also. As the frog makes but little 
exertion either of body or mind, there is but little change in his 
body, and but little nutriment is required to supply the small 
waste that occurs. But in the ever active canary there is 
much waste from this action, and therefore there must be much 
eating to supply the material of repair. As he sings and hops 
from perch to perch, his mind as well as his body is vastly 
more active than that of the frog; and so the particles in his 
brain and nerves, as well as in his muscles, are oftener changed. 
You see the same thing still more strikingly, if you contrast 
11 









122 


HUMAN PHYSIOLOGY. 


Change varies in different parts of the body, and in the same body at different times. 

the torpid state of the hibernating animal in winter, with his 
active state in the warm weather. In his torpid state life is 
dormant, almost at a stand still, sometimes entirely so. Ana 
the more perfect the quiescence, the less is the change, and the 
less, therefore, the need of nutrition. The fat which he lays 
up in the autumn (§ 65) answers all his necessities both for 
nutrition and for heat. 

183. The proportion, thus seen to exist between the amount 
of change and the degree of activity, is exemplified in a com¬ 
parison between different parts of the body. In those which 
are most actively used the change of decay and repair is going 
on most constantly. The active muscles and nerves are con¬ 
tinually changing ; while the bones, which are only passive in¬ 
struments of motion are changed very slowly. And it is a sig¬ 
nificant fact, that in the case of the muscles and nerves, the 
waste particles are to a large extent of the entirely useless kind 
(§ 176), for they are mostly absorbed by the veins, there 
being in them but few lymphatics. That is, whenever we 
think, or feel, or move, we render entirely useless quantities of 
the particles which make up the structure of the muscular and 
nervous systems, and these are got rid of at the proper out¬ 
lets, while other particles immediately take their places. 

184. It is a very prevalent notion in the community, that the 
human body changes throughout once in every seven years. 
But you have seen that the change is very unequal in different 
parts of the body, and is dependent to a great extent on cir¬ 
cumstances. Sometimes very rapid changes occur. Thus, 
when one has been much reduced by sickness, and then on re¬ 
covery quickly regains his usual bulk, the body is very exten¬ 
sively changed in a short period of time. Ordinarily the cir¬ 
cumstance which most influences the change is, as you have 
seen, the degree of activity which exists, whether we look at 
an animal as a whole, or at the tissues separately. 

185. In this constant change going on in the body, life and 
death may be said to be brought into very near companionship. 
Every act of the mind, and every movement of the body breaks 
down some of the structure; and the particles, which are no 
longer fitted to maintain the living functions, must be taken 
away as refuse dead matter, and new particles endowed with 
vital affinities must take their place.. Action, destruction, 
repair, are the successive events which are ever occurring in 
in every part of our frame. Action is followed by destruction, 
and in proportion to its intensity; and repair is necessary to 






CELL-LIFE. 


123 


The formative vessels shown by the microscope to be cells. 

fit for further action. And so through life the nutritive func¬ 
tions are thus struggling against the tendency to decay and 
death, till at length at the appointed limit the struggle is given 
over, the vital affinities release their hold, the common laws of 
dead matter take possession of the body, and the soul passes to 
a world where decay and change are unknown. 


CHAPTER IX. 

CELL-LIFE. 

186 . In previous chapters, in treating of the construction of 
the body, I have spoken of the formative vessels in accordance 
with the common language of physiologists. The common 
idea has been hitherto, that the work of construction is per¬ 
formed by vessels appended to the capillaries. The capillaries 
were considered as the repositories of the blood, they receiving 
it from the arteries, and holding it in readiness for the use to 
which it is to be put by the formative vessels. These formative 
vessels, it was supposed, exercised in some way a power of se¬ 
lection in regard to the constituents of the blood, and also a 
power of uniting the constituents thus chosen into particular 
forms. In this way physiologists accounted for the formation 
of all the different structures in the body. What shape these 
formative vessels had, or how they were arranged no one pre¬ 
tended to know. But of their existence no one had a doubt, 
for there seemed to be an absolute necessity for supposing some 
apparatus of vessels appended to the capillaries for the per¬ 
formance of this function. 

187. But the microscope has of late years revealed pheno¬ 
mena which have changed our ideas on this subject, and 
which must to some extent change our modes of expression in 
relation to it also. It has showed us agencies which differ 
from those which we had supposed to exist. The subject is an 
interesting one, and I propose in this chapter to give you some 
glimpses of this interior life, as it may be termed, of the body, 

188. It is found by the aid of the microscope, that all the 
minute operations of the system are performed by the agency 
of cells. They are not such cells as I described in § 64 as 
existing in the cellular tissue, which are mere interstices, com¬ 
municating together. But they are bladders or sacs, and are 






124 


HUMAN PHYSIOLOGY. 


Cells when first formed globular. Seen in the blood and in most other parts. 

filled either with a fluid alone, or with a fluid containing some 
grains of solid substance, termed molecules. Tiie usual form of 
the cell when it first appears is globular or spheroidal. It is 
seldom, however, seen in this form ; for, besides the change of 
form from the pressure of neighboring cells, the cells them¬ 
selves often change into various shapes, as you will see in 
another part of this chapter. 

1S9. Cells can be seen in the blood. If the web of the foot 
of a live frog be placed under the microscope, you can see 
them sweeping along in the blood vessels, like so many little 
bladders, varying their shape, according as they press on each 
other, or on the sides of the vessel. This is very well repre¬ 
sented in Fig. GO, in which a portion of the web of a frog’s foot 
is seen as magnified 110 diameters. The dark irregular spots 
which you see, as at 3,3, are pigment cells, which give the 
color to the part. 



i 


CAPILLARIES IN THE WEB OF A FROG’S FOOT. 

190. Cells may be seen in most of the fluids besides the 
blood, and also in the solids. The solid parts of animal bodies, 





CELL-LIFE. 


125 


Character and color of tissues dependent on the contents of cells. 


FIG. 61. 


aro composed either of cells, or of structures produced by cells, 
or of a mixture of these structures with cells. The same can 
be said also of plants. Cells, therefore, are the real formative 
vessels in both classes of organized beings. 

191. We have very striking exhibitions of the 
cells in the lower orders of animals. The Hydra, 
a representation of which is given in Fig. 1, 
seems to be made up of little else than cells. 

If you observe under the microscope one of its 
arms, as it moves about, the motion appears to 
be a motion of the cells upon each other. 

There are no fibres to be seen, to which the mo¬ 
tion can be attributed. Fig. 61 represents one of 
these arms highly magnified. The cells, as you 
see, have somewhat of a spiral arrangement. 

192. The character of many of the tissues 
in the body depends on the contents of the 
cells. The cell itself, or the cell-wall, as it is 
termed, is considered to be always the same. 

But the contents vary, and this variation makes 
generally the variation in the character, and in 
the color also, of the various textures. For ex¬ 
ample, all the glands are constructed essentially 
on the same plan; and their difference depends 
upon the contents of the cells in them. Thus 
the liver differs from the tear-gland, chiefly be¬ 
cause the former has cells which fill themselves 
from the blood with the components of bile, while 
the other has cells which fill themselves with the components 
of the tears. The color of various parts, as the iris of the eye, 
the skin of the dark-colored, the hair, &c., depends upon a 
coloring matter, which constitutes either a part or the whole of 
the contents of particular cells. So in plants the various colors 
displayed result from the various coloring matters which cer¬ 
tain cells contain. Some contain yellow coloring matter, others 
red, &c. When various colors appear together in any flower, 
there are, where the colors bound upon each other, cells lying 
side by side which contain different coloring matters. And in 
the shading off of the colors, the effect is produced wholly by 
the variation in the quantities of the coloring matter in the cells. 

193. It is clear from the facts which have been stated, that 
the cells have a selecting power. In the body they take from 
the common pabulum or material, the blood, such constituents 

11* 


l?°°° 


. c ?0 
fooo „\ 
(a oo o\ 

00 0 “ 

10 00 
0 oOO / 
. OOO \ 

fooo OA 
ooy 
. o o 
fo n °o . 

, 0 0 0 \ 

V > 0 0 


CELLS 

In the arm of the 
Hydra. 




126 


HUMAN PHYSIOLOGY. 


Cells absorb and select. Cells real laboratories. 

or substances as they need for their particular purposes. I 
have already given illustrations of this, in speaking of the 
difference in the glands. This selecting power is seen in the 
cells everywhere. Every cell contains its own peculiar consti¬ 
tuents, which it has taken from the blood. For example, there 
are fat-cells which receive fatty matter from the blood, rejecting 
every thing else; pigmentary cells receiving nothing but color¬ 
ing matter from the blood, <fcc. The same thing appears too 
in plants. There are cells which receive from the sap volatile 
oil; others, fixed oil; others, starch ; others, coloring matter, 
Ac. 

194. Fluids, and sometimes gases enter the cells continually. 
The pores through which they enter are not visible even 
through the microscope, but of course such pores must exist. 
Their entrance is controlled by the selecting power to which I 
have alluded. 

195. This selecting absorption thus performed by cells, as 
revealed by the microscope, is one of the most wonderful and 
mysterious phenomena in the material world. There is here 
a power in these cells which is unaccountable. The selection 
is made by the little cell as unerringly, as if its pores were con¬ 
trolled by an intelligence residing there. It has been said that 
this selection is a mere result of affinity ; that a certain affinity 
exists between the contents of the cell; or the cell itself, for the 
constituents which are absorbed. But if it be so, the mystery 
comes no nearer to being solved than before. For how are 
these affinities, so numerous and various, established, and what 
are the principles by which they are governed ? In either 
case the wisdom and power of the Creator may be considered 
as making, in this minute interior life of all organized sub¬ 
stances, some of their most wonderful manifestations. 

196. There is not only a selecting power in the cell, but there 
is often a converting power, by which new compounds are 
formed from the constituents introduced into it. The cell in 
this case, though so small as to be seen only by a microscope 
of considerable power, is a real laboratory, effecting chemical 
changes in its contents. There can often be seen quite a brisk 
movement in the molecules in the cell while these changes are 
going on. 

197. Some cells produce other cells. This is the sole office 
of some of them. In some cases new cells are made by a 
separation of a cell into two or more. A sort of hourglass 
contraction takes place at the middle, by an inflection or fold- 






CELL-LIFE. 


127 


Different offices of ceils. Office of red cells in the blood. 

mg in of the inner cell-wall, for the cell has two walls. At the 
same time the cell becomes elongated. An entire separation 
into two cells is thus, after a little time, effected; and then each 
of these cells becomes two more, and so on. In other cases 
cells are formed within cells. When this takes place, the 
nucleus, that is an aggregation or mass* of solid matter in the 
cell, separates into two different parts, each of which has a cell 
formed around it. 

198. Cells, as you have already seen, do not all perform the 
same office, but there are cells for a great variety of purposes. 
A consideration of these will develope to you still greater won¬ 
ders in the cell-life, and show you in the most interesting man¬ 
ner how great the Creator is in the minute operations of nature, 
as well as in those which are large and obvious to the naked 
eye. 

199. There are different kinds of cells in the blood. There 
are colored and colorless ones. The office of the colorless ones 
has not yet been satisfactorily determined. But we- know more 
about the colored ones. These give the red color to the blood. 
They are not red when looked at singly, but are of a yellow 
cast; and the red color appears only when several are together. 
One office of these colored cells is to carry oxygen to all parts 
of the system, and return the carbonic acid to the lungs to be 
thrown off. By carrying these cargoes back and forth in the 
circulation, these little cells perform a very important office. 
A very valuable part of the cargo of these cells is iron. In low 
states of the system, when the red cells are deficient, the ad¬ 
ministration of iron in some form is often found to be very 
effectual, in connection with a good diet, in remedying the defi¬ 
ciency. The proportion of these red cells varies much in 
different animals. It is largest in those which are the most 
active, and which, therefore, as you saw in the chapter on 
Respiration, consume the largest quantity of oxygen. The 
proportion is greater generally in birds than in the mammalia, 
and it is much greater in the latter than in reptiles or fishes. 
In man it varies much in different individuals. These cells 
are abundant in the ruddy, strong, and active; while it is other¬ 
wise in the inactive, pale, and feeble. 

200. There are cells for absorption, and cells for secretion 


* To the common ear the word mass, which is ordinarily used in relation to aggregates 
of some size, seems out of place when applied to a collection of molecules which is so 
small, that it <* ^ only be seen by a microscope of high power ; but though so small, it is 
to the little *. jntaining it a mass 






128 


HUMAN PHYSIOLOGY. 


Manner in which absorption is performed by cells. 


and excretion. Of these I will give some examples. I have 
said in the chapter on Digestion, that the vessels called lacteals 
absorb chyle from the contents of the intestine. It was formerly 
supposed that they did this through their open mouths on the 
surface of the mucous membrane. But the microscope has 
shown that this is not so. The absorption is accomplished by 
cells, which are developed for this purpose at the extremities 
of the lacteals. They take up the chyle and discharge it into 
the lacteals, and they are dissolved away in the very, act of 
emptying themselves. A new crop therefore of cells appears 
evt-T time the process of absorption is to be performed. And, 
whai is still more curious, every time that absorption is to take 
place, there is cast off, as a preparatory step, a sort of pavement 
of cells ffom over every point in the mucous membrane where 
there is n extremity of a lacteal. The absorbing cells are 
thus uncov .red, so that they can perform their duty. All this 
can be made clear by the following diagram. I must premise 
that the surfac of the mucous membrane of the intestine is not 
a perfectly smo- h surface, but examined by a microscope it is 
seen to be covered with eminences and depressions. Absorp¬ 
tion takes place on the eminences, while the depressions are 
the seats of secretion. In the diagram, Fig. 62 , you have a 

FIG. 62. 



DIAGRAM SHOWING ABSORPTION IN A MUCOUS MEMBRANE. 

representation of the arrangement of one of the eminences 
highly magnified. A, represents it as it is in the intervals 
of digestion when absorption is not going on, and B as it is 
during absorption ; a a are the absorbent vessels or lacteals ; 
b b basement membrane, as it is termed, an exceedingly thin 
membrane acting as a basement to the pavement cells c c ; d d y 

















CELL-LIFE. 


129 


Manner in which secretion is effected by them. 


the absorbing cells. When absorption is not going on, the 
prominence is somewhat shrunken, and the pavement cells 
cover it. There are some granules or small grains, d , in A, 
which are, it is supposed, the germs of the absorbing cells, 
which you see developed in B. When absorption is taking 
place, the prominence is swelled out as represented, the lacteal 
vessels are full, and the absorbing cells appear at their ex¬ 
tremities, while the pavement cells have been thrown off, so 
that the chyle may have free access to the absorbing cells 
through the pores or interstices of the basement membrane. 

201. While absorption thus goes on in the eminences, 
secretion takes place in the depressions. The diagram, Fig. 63, 

FIG. 63. 



DIAGRAM SHOWING SECRETION IN A MUCOUS MEMBRANE. 

represents one of these depressions, or follicles, as they are 
termed, in two opposite states, when secreting, and when not 
secreting. In A, secretion is not going on, and the cells c, in 
the follicle remain quiet. In B, on the other hand, secretion 
is taking place, and it is done by the casting oft of cells, as 
represented. These cells discharge their fluid contents into 
the cavity of the intestine, and disappear, while other cells take 
their places. These follicles are really little glands. And the 
various glands, the salivary glands, the liver, the pancreas, &c., 
are made up essentially of such follicles arranged in different 
ways. You see, therefore, in this diagram, the manner in 
which secretion is effected everywhere. The secreted matter 
is received by the absorbing cells, through the interstices of the 
basement membrane, from the blood in the capillaries which lie 
under this membrane. 

202. The pavement cells, of which I have spoken, cover 
every part of the mucous coat or membrane, and answer as a 
protection to it. There is a similar arrangement over the 
whole outer surface of the body. Next to the true skin is a 
















130 


HUMAN PHYSIOLOGY. 


Muscles made up of cells. Their contraction nnd relaxation. 


basement membrane, and upon these, as in the case of the 
mucous coat of the alimentary canal, lie pavement cells. These 
cells, constituting the cuticle or scarf-skin, are much more 
numerous than in the alimentary canal. There are many 
layers of them. The outer cells dry by exposure to the air, 
and become scales. As these are rubbed otf. the cells below 
take their places ; and there is a constant supply of fresh cells 
from the basement membrane. 

203. There are some cells which are devoted entirely to the 
production of motion, for an ordinary muscle is composed of 
great numbers of chains of cells included in sheaths bound to¬ 
gether. A muscle appeal's to the naked eye to be made up of 
fibres. Each one of these fibres is found by the miscroscope to 
be composed of from 500 to 800 fibrilloe , or minute fibres. 
And each of these fibrillse is a series or chain of cells. In Fig. 
64, a, is represented a fibre as seen under the microscope, 


FIG. 64. 



FIBRE OF A MUSCLE. 

showing the fibrillse of which it is com¬ 
posed. They are separated at the broken 
end by the violence in tearing the fibre. 
In b , you see one of the fibrillse very highly 
magnified, showing that it is a chain of 
cells. In the diagram, Fig. 65, is repre¬ 
sented the condition of a fibrilla in the 
two states of contraction and relaxation. 
In a it is relaxed. In b it is contracted, 
the cells being shortened, and at the same 
time widened. And as all the cells in the 
muscle are thus widened when the muscle 
contracts, we see the cause of the well 
known swelling out of muscles when they 
are in action. That you may form some 
idea of the size of these cells in muscles, 1 
will state that in the space of the square 
of a tenth part of an inch, thus, there 
are over 100,000 of these cells. Q When 


FIG. 65. 
a 


muscular fibril; 

d rt last'd • b contraoitd, 
























CELL-LIFE. 


131 


Hoofs, horns, nuils, and teeth made by cells. 


a large muscle contracts what an innumerable multitude of 
these cells are set in action ! 

204. There are cells whose office it is to make certain solid 
deposits. Hoofs, horns, nails, and teeth are made in this way. 
Even the hard enamel of the teeth is constructed by cells. 
They deposit it in the form of prisms -of hexagonal shape as 
seen in Fig. 66, which represents a vertical section of enamel 
as seen under the microscope. Their shape is more plainly seen 
in A, Fig. 67, which represents a transverse section of enamel. 
The line of these prisms is generally wavy, but they are for the 
most part parallel to each other. At B are some of these prisms 
separated. They are more magnified here than in Fig. 66. 


FIG. 66. 



VERTICAL SECTION OF ENAMEL. 


FIG. 67. 



ENAMEL. 

A, Transverse section. B, Separated prisms of it 


205. Perhaps the most wonderful exhibitions of the functions 
of the cell are presented to us in the nervous system. The 
nerves are bundles of tubes of exceeding fineness. They vary 
from TeVoth to roToTotb of an inch in diameter. Now, each 
of these little tubes, or tubuli, as they are called, was once a 
chain of cells. The cells in each chain or row, as the micros- 








132 HUMAN PHYSIOLOGY. 

Nerves composed of tubes made from cells. Cells in the gray substance of the brain. 


FIG. 68. 



cope has shown, gradually became incorporated together to be¬ 
come a tube, and in this tube is contained the true nervous 
matter. And it is supposed that each of these tubuli preserves 
itself separate and distinct, from its origin in the brain, or some 
other of the central organs of the nervous system, to its ter¬ 
mination in some fibre, or on some surface. For no communi¬ 
cations between the tubuli have ever been found by any micros- 
copist. The manner in which these tubuli are made from cells 
may be illustrated by the diagram 
in Fig. 68, in which the steps by 
which the row of cells A becomes A B 

the tube B are represented. O 

206. It is these tubuli, thus O 
formed from cells, that constitute O 
the means of nervous communica- O 
tion between all parts of the sys- O 
tem. Thus, when a muscle con- o 
tracts in obedience to the will, 

an impression is conveyed through those tubuli that connect the 
brain with the fibres of the muscle, or rather with the cells of 
which these fibres are composed. These tubuli exist in all the 
nerves, and in the white parts of the brain and spinal marrow. 
They transmit, but they have nothing to do with originating 
what is transmitted. This is done by another part of the nervous 
system, the reddish gray substance, which is seen in the brain 
and spinal marrow, as entirely distinct from the white portion. 
This gray substance, in which all nerve force, as it is termed, is 
produced, is made up chiefly of cells. These cells, which have 
a nucleus or central particle, are originally globular, but many 
of them assume various shapes, and often shoot out branches. 
Some of the shapes are very fantastic as represented in Fig. 69. 
These are magnified 200 diameters. 

207. In the views which I have given of cell-life, I have not 
attempted to describe all the phenomena which have been dis¬ 
covered, but only enough of them to give the student a general 
view of this interior unseen life, that is at work so busily at 
every point of every living substance. The cell, you have seen, 
performs a great variety of functions. It is the agent by which 
all vital operations are carried on. The very beginning of life, 
so far as we can see, is in the cell which the microscope reveals 
to us. Its first manifestation is here. We can suppose a germ 
as the origin of a cell, but we do not see it if it exist. 

208. All animated nature is built up by cells. The first 






CELL-LIFE. 


133 


All organized substances built up by cells. 


FIG. G9. 


NERVE CELLS IN THE GRAY SUBSTANCE. 

thing which comes from the supposed germ is a cell. And 
this single cell is the parent of all the cells which build up the 
whole structure, whatever it be. It is by these cells thus pro¬ 
duced, that all plants and animals are constructed. “A globu¬ 
lar mass,” says Carpenter, “ containing a large number of cells 
is formed before any diversity of parts shows itself; and it is 
by the subsequent development, from this mass, of different 
sets of cells, of which some are changed into cartilage, others 
into nerve, others into muscle, others into vessels, and so on, 
that the several parts of the body are ultimately formed. Of 
the cause of these transformations, and of the regularity with 
which they take place in the different parts, according to the 
type or plan upon which the animal is constructed, we are en¬ 
tirely in the dark; and we may probably never know much 
more than we do at present.” 

209. A beautiful exemplification of what has just been stated 
is seen in the development of the animal in the interior of an 
egg, and particularly in the egg of the bird tribe. Bv an ex 

12 






134 


HUMAN PHYSIOLOGY. 


Arrangement of the parts of the egg. 


amination of different eggs at different stages of the process of 
hatching, the various steps in the development of the animal 
have been observed and noted. It is a series of most wonderful 
processes, that go on concealed from our view by that sym¬ 
metrical inclosure of lime. Of these I will present the general 
outlines. In the middle of the egg is the yellow yolk, com¬ 
posed of albumen and oil globules. It is surrounded by an ex¬ 
ceedingly thin sac, which keeps it separate from the albumen, 
the white of the egg that envelopes it. The yolk , b , Fig. 70, is 

FIG. 70. 



lighter than the white, and it therefore always seeks the highest 
point in the egg. But there is a particular contrivance which 
prevents it from actually touching the shell. It is held down 
by two very delicate ligaments e,e, connecting it with the white 
lining of the shell. And you will observe, too, that the cica- 
trieula, or germ-spot, a, which is a collection of cells beginning 
the process which is to form the animal, being lighter than the 
yolk is always at the top of it, in order to receive the warmth 
from the body of the bird as it sets upon its eggs. Besides all 
this, there is at the blunt end of the egg, /, a bubble of air 
which is intended as an invigorating draught for the lungs 
of the young bird, preparatory to its bursting its shell. 

210. When the processes preparatory to the formation of the 
animal commence, the yolk itself is composed in part of cells, 
as represented in Fig. 71, A. In the midst of it there is a 
germinal spot, a, with a vesicle in it, b. This vesicle produces 





















CELL-LIFE. 


135 


Succession of cells in the yolk before the animal is formed. 


FIG. 71. 



DEVELOPMENT OF CELLS IN THE YOLK DURING INCUBATION. 

a cluster of cells. But these cells, and those which in pait 
compose the yolk are temporary, and all disappear. Before, 
however, the cluster of cells in the germinal spot disappear, 
there are seen in the midst of them two twin cells. These 
multiply ; and what is singular, they do it by doubling, so that 
there are successively 4, 8, 16, 32, <fcc. At length there is a 
mass of them, like a mulberry, as at e, in B. This mass then 
sends off cells at its edges which makes a layer,/, all round 
the yolk as represented in C. A second layer, g, is formed 
inside of the first as seen in D. In the case of the higher 
animals a third layer is added. 

211. There is no formation of the animal yet. But now a 
single large cell appears in the centre of the mulberry-shaped 
mass of cells, and from this begins the formation of the animal. 
All the other parts of the egg—the cells, the yolk, the white— 
are tributary to the action which proceeds from this cell. 
Within its wall is a ring-like nucleus. This takes the shape of 
a pear, and then it is afterward very much like a violin. 
From this nucleus are produced cells which form all the 
various parts of the animal, the heart, lungs, stomach, brain, 
limbs, <fec. And these are made out of the yolk and the white 
of the egg. 




136 


HUMAN PHYSIOLOGY. 


Office of the allantois. All animals and plants come from simple cells. 


212. There is one contrivance made use of during this de¬ 
velopment of the animal, which must not pass unnoticed. A 
very delicate bag, called the allantois , is formed, which is attach¬ 
ed to the embryo, and at length almost envelopes it. The office 
of this is to expose the blood of the embryo to the air. This is 
accomplished through the pores of the shell, against w’hich the 
allantois with its minute blood-vessels presses. This organ is 
in fact the temporary breathing apparatus of the developing 
animal. The development can be arrested by smearing over 
the egg with some substance that will prevent the entrance of 
air through the shell. When the animal is fully developed, 
and is ready to come forth from his prison, he inhales the air 
provided for him, as before described, and with the strength 
given to him bj^ the stimulus of the air in his lungs, he bursts 
the crust of lime that incloses him. 

^13. I have described these processes which take place in 
the egg, in order that you may see the mysterious connection 
between the simple cells that form in the beginning, and the 
full development of the complete and diversified organization. 
In the formation of all animals, and we may say plants also, 
there is a similar connection, varied of course according to the 
circumstances of each case. As w'e observe the various steps 
of the process, the mind is filled with wonder. As we look at 
the egg, containing nothing but a yolk surrounded by albumen, 
with its little cell of air at the end, and see it wholly separated 
from every livirg organization, shut up entirely by itself in a 
wall of lime, we can hardly believe that the mere application 
of heat will cause in the contents a series of processes, which 
will result in an animal so complete, that it can burst its own 
prison walls, and, as is the case witir some of the tribe, at once 
walk forth into the open air. The processes by which all this 
is effected have been narrowdy watched by the eager eye of 
scientific inquiry; but the mystery remains unsolved, and pro¬ 
bably to man it will always remain so. 

214. From the views which I have presented in this chapter 
it is manifest, that the grand distinction between organized and 
unorganized substances is to be found in this cell-life of the 
organized. In unorganized substances particles or molecules 
are the only things which we know of as being concerned in 
their formation. But in the construction of organized sub¬ 
stances or beings, every thing is done by the agency of cells. 
And in this cell life of the living world we have another beauti¬ 
ful example of the divers and almost numberless results, which 




CELL-LIFE. 


137 


The power of the Deity shown in the minute operations of Nature. 


the Creator works out by simple and single means. As gravi¬ 
tation holds atoms together in masses of every size from the 
minutest to the largest, and keeps the mighty orbs in their 
appointed circuits, so the cell-organization constructs and moves 
all living things, however small, however large, and however 
diversified. 

215. As we examine the various workings of this cell-life, wa 
can not but perceive the truth of the old adage, Natura in 
minimis maxima est —nature is greatest in its smallest things. 
The power of mere bulk or mere force we can comprehend by 
mental addition, however great that power may be. We can 
imagine a power which we see, to be indefinitely multiplied, 
and thus can form the idea of immense power. But when 
with the microscope we see minute cells working out such 
results as we have contemplated in this chapter, and inquire 
how it is done, we see that there is a hidden power here that 
utterly defies our conception. The mechanics and the chemis¬ 
try of the cell, who can understand them ? From the inscruta¬ 
ble movements of this hidden power, at work wherever life is, 
in the cells, its laboratories, we get a higher idea of Omnipo¬ 
tence than we can get from the grandest and most terrific ex¬ 
hibitions of mere force. We get from them the idea of an all- 
pervading, as well as an all-wise power, working not merely in 
every locality, but at every point of the universe. And the 
revelations which the microscope makes to us seem to draw us 
very near to the Infinite. As we gaze with wonder and delight 
at the secret operations of his power thus opened to us, we seem 
almost to be admitted to his presence; and even our awakened 
curiosity, amid the wonders now brought into our field of vision, 
does not suffice to remove the awe which almost oppresses us. 

216. How great is the inner beauty of the living world 
around us ! We admire the symmetrical forms, and the beau¬ 
tiful colors which nature presents to us in such variety; but 
there is an inner world of beauties throughout nature, still more 
perfect and resplendent, which is hidden from the naked eye 
of man, though it is all open to the Omniscient. If you would 
get some idea of the beauty of this inner world, take the most 
delicately beautiful of all the specimens of man’s workmanship, 
and examine it with a microscope ; and then compare it with 
some living texture or coloring. Compare in this way, for 
example, the most perfect painting of a flower with the flower 
itself. The painting loses all its beauty as it is magnified; but 
in the bosom of the flower the microscope developes to you 

12 * 





138 


HUMAN PHYSIOLOGY. 


The inner beauty developed by the microscope. 


beauties far transcending those which are seen by the unassisted 
eye. Even such living structures as are unattractive to the 
naked eye, present under the microscope wonderful beauty in 
the delicate lines of their textures. It is true of every one who 
has used this instrument in his observation of nature, that he is 
impressed with the fact, that great as is the beauty of nature, 
as we look out upon it, it is vastly inferior both in kind and in 
amount to that inner beauty seen so completely by the all- 
seeing Eye, and now developed to us in part by the skill and 
ingenuity of man. And it suggests to us the hope, that in a 
new state of being, and with higher faculties, we shall be able 
to look farther into these inner beauties of the universe, than 
we now can with all the aids which our ingenuity can devise. 




PART THIRD, 


CONTAINING 



Voice. CHAPTER XV.-The Ear. CHAPI 
Connection of the Mind with the Bodv. 
Man and the inferior Animals. CHAP! 
CHAPTER XX.— Life and Death. 


: Body. CHAPTER XVIII. — Differences between 
CHAPTER XIX. —Varieties of the Human Race. 


CHAPTER X 


THE NERVOUS SYSTEM. 


217. Thus far we have contemplated man merely as a struc¬ 
ture. We have observed the means by which the body is 
built and is kept in repair. We have seen that in regard to 
these functions of nutrition, man and all animals have much in 
common with plants. So far as these functions are concerned, 
they vary from plants only in the modes by which the nutrition 
is effected. The difference in this respect is not an essential 
one. The absorbents in the root of the plant do for the plant 
what the lacteals in the digestive organs do for the animal, 
the difference between them being only according to the 
differing circumstances. So also, circulation and formation are 
in all essential points the same in these two different depart¬ 
ments of animated nature. The microscope has in the most 
striking manner shown this to be true of formation, for vegeta¬ 
bles and animals are alike constructed, as you have seen, by 
cells. 

218. The functions of which I have treated in the previous 
chapters, as being common to plants and animals, are called the 
functions of organic life, because they concern merely the struc¬ 
ture, the organization. But there are other functions. The 
body, with all its complicated parts, is constructed and kept in 
repair for certain uses. These uses are secured by the nervous 
system,—a system, which I have spoken of in § 32, as being 
superadded to what the animal has in common with the plant, 
and which, therefore, constitutes the essential difference between 
the animal and the plant. This system furnishes the means 
of the relations of the animal to the world around him. Ho 
receives his impressions from external things through this 



140 


HUMAN PHYSIOLOGY. 


The nervous system and its subordinate instruments. 

system; and through it he acts upon external things. He 
feels through the nerves, and by the nerves excites those 
motions by which he acts on both material and immaterial 
existences. The functions, therefore, which are performed 
through this system, are called functions of animal life, in dis¬ 
tinction from the functions of organic life, which are common 
to vegetables and animals. They are sometimes also called 
functions of relation, in view of the relations which it estab¬ 
lishes between sentient and moving beings, and all external 
things. 

219. But there are intermediate instruments, through which 
the nervous system exercises its functions. The nerves do not 
themselves move, but they excite motion in muscles, and these 
move bones and other parts. Neither is sensation performed 
by the nerves alone. The different senses, for example, have 
different organs, with arrangements differing according to the 
kind of sensation. Mere nerves do not alone see, or hear, or 
taste, or smell, or touch. There are special organs constructed 
for these purposes; and through these the nerves receive im¬ 
pressions. Thus the nerve of sight cannot of itself see; but 
the eye being there, so formed as to have pictured on a mem¬ 
brane the images of objects, the nerve receives an impression 
from these images, and this impression is transmitted through 
the trunk of the nerve to the brain, where the mind takes cog¬ 
nizance of it; and this constitutes seeing. 

220. While then the nervous system is the great essential 
means of connection between the mind and external things, 
there are other subordinate means, as we may consider them. 
They are organs of various kinds, through which the nerves act 
and are acted upon. The nervous system, therefore, may be 
viewed as presiding over the sentient and moving machinery, in 
the complex structure of the human system, which we have 
been examining in the previous chapters. 

221. The nervous system in the lower orders of animals is 
very simple, and forms an exceedingly small part of the animal. 
But, as we rise in the scale, we find that, as the limits of rela¬ 
tion to external things enlarge, this system becomes more 
prominent; till, in man, in whom these relations, both mental 
and physical, are much more extensive than in any other 
animal, it is very prominent and greatly complicated. 

222. The interest of the class of subjects, now to be opened 
to you, much transcends that of the subjects which we have 
already gone over. If you look at a child as it first opens its 




THE NEKYOUS SYSTEM. 


141 


AH knowledge acquired and communicated by nerves. 

eyes upon this world, you see a being, whose senses are com¬ 
mencing their work as inlets of knowledge to the soul within. 
Nothing is known at the outset, of shapes, or colors, or dis¬ 
tances, or any other relations of things. This is all to be 
learned, through the nerves and their subordinate organs. And 
as all knowledge is acquired through the nerves, so it is com¬ 
municated through nerves to others. It is communicated by 
the motions that are excited in the muscles by the nerves—the 
motions of the countenance varying its expression ; the motions 
of the limbs, or gestures ; but especially by the motions which 
produce and articulate the voice. Thought and feeling can be 
communicated in no other way than by muscular motion. 

223. From what has now been said, you readily see, what 
will be the subjects of the third part of this book. They are 
those which relate to the nervous system and its connections or 
dependencies. They are, the nervous system itself; the organs 
of locomotion, the muscles, and the bones; the voice ; the ex¬ 
pression of the countenance, and the language of the muscles 
generally ; the senses, with their organs; instinct; thought; 
reason. 

224. As preparatory to a particular view of these subjects, I 
will give you a general view of the nervous system, with the 
functions performed by the various parts of it. I shall reserve 
for another chapter a particular view of some of the higher 
functions of this system, and a consideration of some subjects, 
which we can better examine after we have considered the 
organs of locomotion and the senses. 

225. The nervous system may be considered as having 
three parts; 1, certain central parts, as the brain and spinal 
marrow; 2, nervous trunks, which going from these central 
parts divide and subdivide, as the arteries do, till they become 
exceedingly minute; and 3, the nervous expansion in the 
organs, having a relation to the nervous trunks similar to that 
which the capillaries bear to the arteries. In what we call sen¬ 
sation we suppose that an impression is produced in the nerv¬ 
ous expansion, that the trunk serves to transmit it, and that 
through the nervous centre, the brain, it is communicated to 
the mind. 

226. Let us see now what is necessary to this compound act, 
termed sensation. First, it is necessary that the organ where 
the nerve is expanded be in a condition to let the nerve receive 
the impression. If the eye be so injured in its textures, that 
the impression can not be made on the nerve, there can be no 




142 


HUMAN PHYSIOLOGY. 


Necessary conditions of nervous action in sensation and motion. 

vision. So, too, of the other senses. Taste ancl smell are often 
impaired, sometimes even destroyed for a time, by an inflam¬ 
mation of the mucous membrane, on which the nerves devoted 
to these senses are expanded. This is sometimes the case in a 
common cold. It is necessary also, that the trunk of the 
nerve be in a proper condition. If the nerve of vision be 
pressed upoii by a tumor, there will be no impression trans¬ 
mitted from the images formed in the eye. So, too, if a nerve 
going to any part of the body be cut off, there can be no trans¬ 
mission of impressions to the brain from that part. Again, it 
is necessary to sensation, that the brain should be in a state to 
communicate the impression to the mind. If the brain be 
pressed upon strongly by a depression of the skull from 
violence, or by effusion of blood by the rupture of an artery, as 
sometimes occurs in apoplexy, there can be no sensation. 
Excitement of mind, too, sometimes prevents the occurrence of 
sensation, by its action upon the connection between the mind 
and the brain. The pain of a wound received in battle is often 
unfelt, until the excitement of the battle is over. The aching 
of a tooth is often stopped by the excitement consequent upon 
going to the dentist to have it extracted. I onpe burned my 
hand in the beginning of a chemical lecture, but felt no pain 
till I had finished it, and then the pain was at once very 
severe. In these cases the cause of the pain is acting all the 
while upon the nervous extremity, and the trunk of the nerve 
is capable of transmitting the impression, but the state of the 
mind is such, and such is the consequent condition of the 
brain, that the sensation does not occur—one link in the neces¬ 
sary chain is defective. 

227. The same can be said, in regard to the necessity of 
each of these links of the chain, in relation to voluntary mo¬ 
tion, as well as sensation. The brain must be in a condition 
to be acted upon by the mind; the nervous trunk must be 
capable of transmitting the impression ; and the muscle must 
be in such a state, and in such connection with the extreme 
nervous fibres, that it can respond to the call of the brain. 

228. Before going further, I will give you some idea of the 
proportions and arrangement of the central organs of the 
nervous system. In Fig. 72 you have presented a general 
view of this system,—the central organs with the nerves going 
out from them. At a is the cerebrum, the upper large brain, 
filling up a considerable portion of the skull; at b is the 
cerebellum, the lesser brain, lying beneath the cerebrum at its 




THE NERVOUS SYSTEM, 


143 


General plan of the nervous system. 


FIG. 


' 2 . 



FERVOUS TRUNKS IN MAN. 









144 


HUMAN" PHYSIOLOGY. 



Hemispheres and lobes of the brain. 

back part: at c is the great facial nerve, the chief nerve of the 
face; the spinal marrow, d , sends off branches on either side 
in its whole length; at e is the brachial plexus, a bundle of 
nerves coming from the spinal marrow, which here unite 
together, and are then distributed to all parts of the arm ; at i 
is a similar plexus from which are distributed nerves to the 
lower extremity; /, g, and h point to different nerves in the 
arm, and Z, m, n, and o to different nerves in the leg. You 
observe that the whole of this nervous system is divided into 
exactly similar halves. The cerebrum and the cerebellum are 
both double organs, and the nerves of one side are just like 
those of the other. 

229. Having thus observed the general arrangement of the 
nervous system, I call your attention next to the arrangement 
and structure of the brain which are seen in Fig. 73. This 

FIG. 73. 


BRAIN AND NERVES. 

Figure presents to view a perpendicular section of the brain, as 
made from front to rear, dividing it into two halves. You 
have here a view of the inner surface of one hemisphere, as it is 








THE NERVOUS SYSTEM. 


14* 


Cerebrum. Cerebellum. Convolutions. Membranes. 

termed, of the cerebrum, the large upper brain, which is com¬ 
monly described as having three lobes or divisions, a, the 
anterior; b, the middle; and c the posterior. At / is the 
broad band of white fibrous matter, which unites the two 
halves or hemispheres together, of course divided in the 
section ; at d is the cerebellum showing a peculiarly beautiful 
arrangement, called the arbor vitce , or tree of life; at g is the 
beginning of the optic nerve which goes to the eye; l is the 
nerve of smell; e is the commencement of the spinal marrow. 
The many nerves which you see, are distributed to various 
parts of the face; the nerve at h goes to the tongue; at i to 
the throat, and at m to one of the muscles of the eye. From 
the beginning of the spinal marrow go forth many nerves, one 
of which, k, is a very important one, as it sends off branches to 
the lungs, the heart, and the stomach. It is this part of the 
nervous system, the top of the spinal cord, that it is most im¬ 
mediately essential to the continuance of life. For it is by 
their nervous connections with the top of the spinal marrow, 
that the heart and lungs continue to perform their duty. It 
has been ascertained, by experiments upon animals, that the 
cerebrum, and even the cerebellum, can be destroyed, and yet 
the animal will continue to breathe, and the circulation will go 
on for some time. But the moment that this part of the 
spinal cord, from which the heart and lungs are supplied with 
nerves, is destroyed, the breathing and the circulation stop 
and the animal dies. So, too, in apoplexy, if the effusion of 
blood lake place at the top of the spinal marrow, death will 
occur more certainly, and in much shorter time, than if the 
effusion take place in the cerebrum or cerebellum. 

230. You observe that the cerebrum has deep irregular 
furrows on its surface, and that it presents undulating tortuous 
projections. These are called the convolutions of the brain. 
Into the furrows between them dips down the membrane, in 
which branch out the arteries that supply the brain with blood, 
and the veins that return it from this organ. This membrane 
is from its soft and delicate texture, called the pia mater (pious 
mother) while the stout fibrous membrane, which lies outside 
of this next to the bony covering is called the dura mater , or 
hard mother. The names are entirely inappropriate, for the 
latter serves as a protection to the brain, and the former is 
merely a vehicle or medium for the entrance of the blood 
vessels into the brain. There is another membrane lying 
between these which is called the arachnoid membrane, be- 
13 







146 


HUMAN PHYSIOLOGY. 


Gray and white substance. Proportions and arrangement. 


cause in its tenuity and delicacy it resembles the spider’s 
web. It is one of the serous membranes, and it serves as a 
protecting envelope to the brain, and at the same time by its 
serum, keeps this organ bedewed with moisture over its whole 
surface. 

231. The substance of which the brain is composed is very 
soft, something like blanc-mange. It is the softest organ in 
the body. It is not uniform throughout in color. All around 
the white inner part of the brain there is a thick layer of gray 
substance. In Fig. 74 you have a horizontal section of the 

FIG. 74. 



SECTION OF THE BRAIN. 


brain, showing the proportions and arrangement of the gray 
and the white substances. As the gray substance dips down, 
as you see in the figure, into all the furrows, its extent is 
greater than you would suppose at the first view. In the 
middle is represented the broad connection which exists 
between the two hemispheres of the brain. You observe in 









THE NERVOUS SYSTEM. 


147 


The gray substance made of cells, the white of tubes. 


Fig. 73, and Fig. 74, that there is no apparent arrangement of 
the external parts of the brain, which would give countenance 
to the idea of the phrenologist, in relatiomto a division into 
particular organs. The convolutions, so far from presenting 
any well defined arrangement, are exceedingly irregular. 

232. The gray substance, which is sometimes called the 
cortical (bark-like) substance, because it surrounds the white 
central part of the brain, is made up, as I said in the Chapter 
on Cell-Life, § 208, of cells, while the white part is composed of 
exceedingly minute tubes. These tubes are continued into the 
nerves, and as they hold the nervous matter, they constitute the 
medium of communication between the brain and all parts of 
the body. This function of communication is the sole function 
of the white nervous matter. In the brain this white matter is 
a mere collection of tubes, and these branching out in bundles 
form the nerves. These tubes are supposed to be entirely 
separate from each other, from their beginning in the brain to 
their termination in the various parts of the body, for the 
microscope, as stated in § 205, has never discovered any union 
between them at any point. The brain then is a great central 
organ of communication, where innumerable minute tubes are 
brought together, each of which is connected with some one 
moving fibre, or some one sensitive point in the body. Those 
which are connected with mus¬ 
cular fibres transmit impres¬ 
sions from the brain, and FIG * 75 - 



those which are connected 
with sensitive points transmit 
impressions to it. Of the 
size of these tubes you can 
judge by Fig. 75, which 
shows some of them as they 
appear magnified 350 diam¬ 
eters. They vary much in 
size, but the cause of this 
variation has not been dis¬ 
covered. 


233. The office of the gray 
substance, it is quite well 
ascertained, is very different 


NERVOUS TUBULI, 
Magnified 350 diameter* 


from that of the white sub¬ 
stance, as the difference in 

its structure would lead us to suppose. It is more nearly 











148 


HUMAN PHYSIOLOGY. 


Office of the gray substance. Proportioned to the amount of intelligence. 

connected with the mind than the white substance. When, 
for example, motion is produced in obedience to the will, the 
impression producing the motion is transmitted through the 
white matter, but the cause of this impression does not act 
directly on this matter. The impression is caused by the 
action of the mind on the gray matter, and the white substance 
only serves to transmit it. The gray matter, therefore, has a 
more active agency than the white in the phenomena of the 
mind and the nervous system. It is the first link in the chain 
of connection between the spiritual and the physical* in our 
nature. Hence, in examining the brains of animals, we find 
that the higher is the intelligence, the more abundant is the 
gray substance; and it is especially abundant in man, by the 
large development of the convolutions. 

234. The question arises here, whether, as in motion the 
active agency is on the part of the gray matter in the brain, 
f here is also gray matter at the extremities of the nerves of 
sensation, exerting an active agency there. It would seem that 
it should be so. When voluntary . motion is produced, the 
action of the mind is on the gray substance, and the white sub¬ 
stance of the brain and the nerves transmits the impression of 
this action. But in sensation the first step in the process is not 
in the brain, but in the nervous extremities. Now in this first 
step, in the actual production of the impression to be trans¬ 
mitted to the brain, we should suppose the gray matter as 
necessary as in the production of the impression to be trans¬ 
mitted from the brain in effecting voluntary motion. Else we 
must conclude, that, while the white substance can have no 
active agency in the brain, but serves only for transmission, at 
its other extremity, expanded in the organs, it serves for both 
transmission and production. Dr. Carpenter supposes, there¬ 
fore, that there is a sort of gray matter in the expanded extrem¬ 
ities of all nerves of sensation. But the microscope has never 
discovered the existence of this matter in any nervous expan¬ 
sion, except in the nerve of the eye, in the retina, and in some 
parts of the internal ear. And some facts seem to militate 
against Dr. Carpenter’s view of the subject. If, for instance, 
you hit the trunk of a nerve, as the little nerve so often hit at 
the elbow, a sensation is produced, which is in some measure 
referred to the part to which the nerve is distributed. From 
such facts it would appear, that in sensation the white nervous 
matter does not merely transmit impressions, but has an 
agency also in originating them. There is then probably 




THE NERVOUS SYSTEM. 149 

The gray substance well supplied with arterial blood. Ganglions and plexuses. 


no gray matter ordinarily in the expanded extremities of a 
nerve, but they are merely terminations of the tubes which 
make up its trunk. 

235. The cells which form the peculiarity of the structure <_f 
the gray substance are often, as you saw in Fig. 69, of very 
singular appearance from their prolongations. They lie in the 
interstices of a vascular network. A due supply of arterial 
blood is absolutely essential to the vigorous performance of the 
functions of the gray substance. If the supply be cut off in 
any way, as by the failure of the heart’s action in fainting, 
insensibility and the loss of the power of motion are the conse¬ 
quence. While the gray substance is on the outside of the 
brain, it is on the inside of the spinal marrow. It is also on 
the inside of the little bodies called ganglions, scattered hero 
and there, as depositories of nervous force, or as little brains, as 
we may term them. These ganglions are not merely a part of 
the apparatus of communication. They are different from 
plexuses, which are mere combinations of nervous trunks, as 
seen in Fig. 77, t t being the trunks, which, after uniting with 


FIG. 7G. 




each other in various ways, again separate to go to their 
different destinations. At g , in Fig. 76, is a ganglion into 
which the fibres f of the nerve n run. It then divides again 
into branches b. These ganglions 'produce nervous force, and 
therefore are composed like the brain in part of gray substance. 
The spinal marrow, too, produces as well as transmits, and so 

13 * 




















150 


HUMAN PHYSIOLOGY. 


Changes in the nerve-cells. Termination of the nervous fibres. 

this substance forms a part of it. This gray substance, as it is 
in constant operation, is subject to much wear and tear, as we 
may express it, and therefore the changes of repair are con¬ 
stantly going on in its structure. Hence, the necessity for so 
large a supply of blood, as is secured by the network of vessels, 
among which the cells peculiar to this substance are scattered. 
The microscope has fully demonstrated the reality of these 
continual changes, for it shows us, whenever a portion of this 
substance is examined by it, the cells in all the various stages 
of development mingled together. The freshly made simple 
cells are seen among those which have been formed for some 
time, and which have put forth their long off-shoots, as seen in 
Fig. G9. 

236. The extremities of the fibres, or rather of the tubuli 
(Fig. 75) of the nerves terminate variously. The most common 
termination is in loops, as seen in Fig. 78, which represents the 



NERVES OF TOUCH IN THE SKIN OF THE THUMB. 


termination of the nerves as seen through the microscope in 
a thin perpendicular section of the skin in the thumb. The 
three eminences in this figure are those of the 'pa-pillce , as they 
are termed, which you can see are arranged in curvilinear rows, 
if you look at the ball of the thumb. In Fig. 79 you see this 
same loop-like arrangement in the nervous tubuli, as seen 
through the microscope, on the sensitive sac that lines the 
cavity of a tooth, the entrance for the nerves and bloodvessels 
of this sac being at the end of the root. 

237. One very singular termination of the nervous tubuli, is 
in what are called Pacinian corpuscles, after Pacini, the first 
microscopist that discovered them. They are found attached 
to the nerves in the hand and foot more often than any where 













THE NERVOUS SYSTEM. 


151 


Pacinian corpuscles. ^Their office not known. 


FIG. 79. FIG. 80. 



else. Their structure, which is seen in Fig. 80, A, highly- 
magnified, is very curious. They are attached to the branches 
of the nerves on which they cluster by little peduncles or 
stalks. At a is the peduncle; b is the nervous fibre or 
tubulus; f is its termination in the corpuscle. The corpuscle 
itself is composed of layers of a very delicate fibrous membrane 
inclosing each other like the coats of an onion, to the number 
of sometimes sixty, the inner ones, d , being closer together than 
the outer ones, c, are. In B is represented a portion of a 
nerve of a finger, with clusters of these corpuscles of about the 
natural size. Of what use these singular bodies are we know 
not. But the fact that they are always found in certain 
regions of the body shows that they are placed there for some 
definite purpose. It has been supposed by some that they are 
minute electrical batteries, because they bear some resemblance 
to the electrical organs found in some fishes. 

238 There is a wonderful fact in regard to the healing of 
wounded nerves which must not pass unnoticed. You know 




































































152 


HUMAN PHYSIOLOGY. 


Healing of nerves. Nice fitting of the tubuli. 

that if a nerve be divided, all communication between the part 
that it supplies with branches and the brain is cut off. No 
impressions can be transmitted through it to and from the 
brain. But the two cut ends of the nerves can grow together, 
and the communication can thus be more or less restored. 
Sometimes it is as perfect as before. Now, if you call to 
mind the structure of a nervous trunk, you will see that this is 
passing wonderful. It is made up, you will recollect, of tubuli 
which are entirely separate from each other, and each one 
of these goes from its origin in the nervous centre to its 
destination by itself. It is difficult to conceive, therefore, how 
the nerve can be healed without creating confusion. For to 
avoid this it would seem to be necessary, that each little tube 
at its cut end must unite with its corresponding end, and not 
with the end of some tube with which it has no relation. For 
example, if the nerve distributed to the hand were cut, it 
would not do, as it seems to us, to have tubuli which go to the 
thumb unite with those which go to a finger. And besides, as 
I shall soon show you that the tubuli, through which the 
impression that produces motion is transmitted, are separate 
from those which transmit the impression that causes sen¬ 
sation, it would not do for a tubulus of one kind to unite 
in the healing with one of the other kind. We can not 
conceive how a confusion in sensations and motions can be 
avoided, unless the end of each fibre or tubulus is united 
with its corresponding end; and such an accurate union 
of the multitude of tubuli in a nerve seems an impossibil¬ 
ity. That there is, however, a very accurate union effected, is 
manifest from the observations of M. Brown Sequard. He 
examined in animals nerves which were divided twelve months 
before, and could not discover the point of division even with 
the aid of the microscope. If the tubuli were not all made as 
perfectly continuous as before the nerve was divided, the 
microscope would have revealed the defect. But it takes time 
to effect this adjustment of the tubuli, for it was found by Dr. 
Haighton in his experiments nearly fifty years ago, that after 
dividing nerves, their functions were not restored till some 
time after they were apparently healed. This shows most 
clearly, that the arrangement of the tubuli, which is required 
for the communication of impressions through them, is gradu¬ 
ally effected after the union takes place. 

239. Taking this view of this interesting point, the difficulty 
is greatly enhanced, when we look at the union of parts that 





THE NERVOUS SYSTEM. 


153 


Nerves of the spinal marrow compound. 

did not originally belong together, as, for example, when a 
piece of skin is dissected from the forehead, and is twisted 
down so as to be made to grow on to the nose to supply 
a deficiency there. Here new relations entirely are established 
between the nerves of the divided parts, and, as we should 
expect, there is confusion in the sensations. The patient, at 
first, whenever the new part of his nose is touched refers the 
sensation to the forehead. But this confusion of the sensations 
is after a while removed. And it is curious to observe, that 
while the old nervous connections are breaking up, and the 
new ones are becoming established, there is an interval of 
partial, sometimes entire, insensibility in the part. How these 
new relations can be established consistently with the known 
arrangement of the tubuli in the nerves is a mystery. 

240. As I have already hinted, there are different nerves for 
different purposes. The nerves through which the mind sends 
its messages to the muscles, are not the same with those 
through which it receives impressions in sensation. In and 
about the face, the nerves of motion and sensation are, for the 
most part, entirely separate from each other. But in other 
parts of the body, the fibres or tubuli for motion and sensation 
are mingled together in the same nervous trunk, inclosed in 
one sheath. It is found that each of the nerves, coming out 
from each side of the spinal marrow, has two roots, which 
unite together and are inclosed in one sheath. 

This arrangement is represented in Fig. 81, 
in which a is a portion of the spinal cord; 
d the anterior root; b the posterior root; e 
the trunk formed by the union of these two 
roots ; and / a branch of the nerve. At c, 
on the posterior root is one of the ganglions, or 
little brains, of which I spoke in § 235. 

Why they are placed on these posterior roots, 
and not on the anterior, or why they are 
placed here at all, we know not. It has 
been ascertained by many experiments on 
animals, that the posterior roots are composed 
of tubuli, which bring impressions to the spinal marrow; while 
the anterior are composed of tubuli which carry impressions 
from the spinal marrow. For, if the spinal cord of an animal 
be laid bare, and a posterior root be irritated, pain is produced; 
but if an anterior root be irritated, violent motions are caused 
in the parts to which the nerve is distributed. That is, the 


FIG. 81. 


a 



‘ d f 


SPINAL CORD. 






154 


HUMAN PHYSIOLOGY. 


Different nerves for different offices. 


posterior root is a nerve of sensation, and the anterior a nerve 
of motion. It is a mere matter of convenience that they unite, 
and are mingled together in the same sheath, for they are to 
be distributed in the same parts. In and about the face the 
nerves of motion and sensation are kept for the most part 
separate, as before stated, merely because it would be no con¬ 
venience in any case to put them together in one sheath. 

241. But not only are there different nerves for sensation 
and for motion, but there are also different nerves for different 
kinds of sensation. Thus, in the eye, the optic nerve which 
transmits the impressions from the images formed on the 
retina, as will be shown in the Chapter on the Eye, is wholly 
separate from the nerve by which any pain or irritation is felt 
in this organ. The latter is called a nerve of common sen¬ 
sation—the former a nerve of special sensation. So in the 
nose, the nerve that takes cognizance of odors is a different 
one from that by which irritation on the same membrane is 
felt. The snuff-taker smells the snuff with one nerve, and feels 
its tingling with another. 

242. The nerves devoted to one kind of sensation can not in 
any case perform the function of those of any other kind. 
Each nerve is fitted for its own peculiar office, and has for this 
its own peculiar susceptibility. Thus, the nerve of touch is 
insensible to light, and, on the other hand, the nerve of vision 
is insensible to touch. If, therefore, the nerve of vision be 
paralyzed, but the nerve of common sensation in the eye be 
unimpaired, although there is no seeing, the eye is as sensible 
to irritation as ever. On the other hand, if the nerve of vision 
be unimpaired, and the nerve of common sensation be par¬ 
alyzed, as sometimes happens, the individual can see, but he 
has lost the sentinel that stands guard over the eye, and by its 
warning of pain keeps it from injury. What, therefore, is 
flying in the atmosphere may lodge in the eye, and though it 
produce no pain, it will excite inflammation by irritating the 
capillaries. The eye in some of these cases is destroyed, 
by the inflammation which thus arises from the loss of sensi¬ 
bility to the touch. When the nerve of common sensation is 
in a healthy state, the moment any thing gets into the eye 
great pain is produced, and the tears flow and the eyelids are 
in constant motion; and if by these instinctive means, as we 
may term them, the irritating substance is not removed, other 
means are at once resorted to. But when this nerve is par¬ 
alyzed, although the irritating substance produces no pain, it 




THE NERVOUS SYSTEM. 


155 


Different degrees of sensibility in the various parts of the body. 

gradually causes inflammation in tlie delicate vascular texture 
of the eye. Pain, then, in this case, as well as in every other, 
is a safeguard against danger. The part is endowed with an 
acute sensibility to touch, because it is needed as a sentinel in a 
part so delicate and yet so exposed. 

243. This leads me to remark, that the different parts of the 
body are endowed with different degrees of sensibility, accord¬ 
ing to their necessities, in relation to the warning of danger. 
Accordingly, the skin is the most sensitive part or organ of the 
body, that it may warn at once of the approach of danger; 
while the internal parts have much less sensibility, some of 
them none. In the performance of operations, therefore, the 
great suffering is in the cutting of the skin. There is very 
little sensibility in the muscles, and there is none in the bones. 
The following fact illustrates the use of the sensibility of the 
skin in the prevention of injury. A man who had lost all 
sensibility in his right hand, but retained the power of motion, 
lifted the cover of a pan when it was burning hot. Although 
he was not aware of any effect at the moment, the consequence 
was the loss of the skin of the fingers and of the palm of the 
hand, laying bare the muscles and tendons. If the sensibility 7 ' 
had not been lost, that is, if the nervous tubuli which transmit 
sensation had not been paralyzed, the warning of pain would 
have been instantly given to the brain, and orders would have 
been sent to the muscles to relax their grasp of the cover; and 
so rapid are these transmissions, that the cover would have 
been dropped soon enough to prevent any great amount of 
injury from being done. 

244. Although there is so little sensibility in the internal 
parts in their healthy condition, yet when they become inflamed 
they become sensible of pain, sometimes acutely so. Thus, an 
inflamed bone is the seat of severe pain; and the tendons, 
although nearly insensible ordinarily, become very painful 
when inflamed, as any one that has a deep-seated felon can 
testify. The question as to the cause of this change of sen¬ 
sibility I will not stop to discuss, but that there is a benevolent 
object in it is very manifest. If inflammation caused no pain 
in such parts, it might go on to a destructive extent without 
the person’s being aware of the danger, and therefore without 
his applying for medical means. 

245. It was formerly supposed that a nerve must of course 
have an exquisite sensibility. But there is no sensibility in 
nerves devoted to motion. Neither is there any in the brain 





156 


HUMAN PHYSIOLOGY. 


Insensibility of the heart to the touch. Respiratory nerve of the face. 

itself. Portions of it can be cut off without producing any 
pain. The heart, too, is insensible to the touch. A case 
proving this fell under the observation of Harvey, the dis¬ 
coverer of the circulation of the blood. A young nobleman, 
from an injury received in a fall, had a large abscess on the 
chest, which occasioned such a destruction of the parts, as to 
leave the lungs and heart exposed. Charles I., on hearing of 
the case, desired to have Harvey see it. “When,” says 
Harvey, “I had paid my respects to this young nobleman, and 
conveyed to him the king’s request, he made no concealment, 
but exposed the left side of his breast, when I saw a cavity, 
into which I could introduce my fingers and thumb; aston¬ 
ished with the novelty, again and again I explored the wound, 
and first marveling at the extraordinary nature of the case, I 
set about the examination of the heart. Taking it in one 
hand, and placing the finger on the wrist, I satisfied myself 
that it was indeed the heart which I grasped. I then brought 
him to the king, that he might behold and touch so extraordi¬ 
nary a thing, and that he might perceive, as I did, that unless 
when we touched the outer skin, or when he saw our fingers 
in the cavity, this young nobleman knew not that we touched 
his heart!” This absence of sensibility in the heart is not 
because it is not well endowed with nerves. It is well 
endowed, but it is with nerves which are devoted to another 
purpose. They are nerves of sympathy, which establish a 
connection with every part of the body, making this organ to 
be so easily affected by motion, by disease, and by every pass¬ 
ing emotion in the mind. 

246. In the face we have an example of different sets of 
nerves for different classes of motions. All those motions that 
are used in the expression of the countenance are associated 
together by a certain nerve. This nerve has nothing to do 
with other motions, as mastication. Other nerves are provided 
for them. Sometimes this nerve of expression is paralyzed on 
one side. The result is, that while the individual can masti¬ 
cate equally well on both sides, he can laugh, and cry, and 
frown, only on one side, and he can not close the eye on the side 
affected. In Fig. 82 is a representation of this condition of 
things. The left eye can not be closed by any effort, and the 
left side of the face is wholly devoid of expression. This nerve 
of expression is often paralyzed by itself, the other nerves in the 
neighborhood, both nerves of sensation and of motion, being 
entirely unaffected. This nerve has been called the respiuitory 





THE NERVOUS SYSTEM. 


157 


Paralysis of the respiratory nerve of the face. 
FIG. 82. 



PARALYSIS OF THE NERVE OF EXPRESSION 

on one side of the face. 

nerve of the face, because it controls motions which are con¬ 
nected with the movements of respiration. If you observe how 
the various passions and emotions are expressed, you will see 
that there is a natural association between the muscles of the 
face and those of the chest in this expression. This is very 
obvious in laughing and in weeping. But this association can 
be effected only through nervous connections. And these con¬ 
nections in this case are very extensive and intimate. When 
the nerve of expression, or facial respiratory nerve, is par¬ 
alyzed, all the motions of the face connected with the respi¬ 
ration are absent. Though the individual may sob in weep¬ 
ing, or send forth the rapid and successive expirations of 
laughter, yet the face on the side where the nerve is par¬ 
alyzed will be perfectly quiescent. So, too, those movements 
of the nostrils which are sometimes used in expression, can 
not be performed. Sneezing and sniffing up can not be dono 

14 








158 


HUMAN PHYSIOLOGY. 


Nerves of the eye. Paralysis affecting different nerves. 

on the affected side. Neither can the individual whistle, 
because a branch of this nerve goes to the muscles at the 
corner of the mouth, which are therefore disabled. Sir 
Charles Bell, in cutting a tumor from before the ear of a 
coachman, divided this branch of the nerve. Shortly after, tlnj 
man thanked him for curing him of a formidable disease, 
but complained that he could no longer whistle to his horses. 

247. The eye has six different nerves, each for a different 
service. 1. The optic nerve. This has nothing to do with the 
motions or the common sensations of the eye. Its sole office is 
to transmit impressions from the images formed in the eye to 
the brain. 2. A nerve of common sensation, by which any irri¬ 
tation in the eye is felt. 3. A nerve which is distributed to the 
muscles of the eye generally, and to no other parts of this organ. 
4. A nerve which goes to one particular muscle, one of the oblique 
muscles of the eye. It is an involuntary muscle which performs 
the insensible rolling motions of the eyeball, and is associated 
with the muscles of expression in the countenance by means of 
nervous connections. 5. A nerve which goes to another single 
muscle, which turns the eye outward. 6. A branch of the 
respiratory nerve, which regulates the motion of the eyelids, 
and has much to do, therefore, with the expression of the coun¬ 
tenance. To this small organ, then, are distributed six different 
nerves, each having its distinct office, and its separate origin in 
the brain. How various are the transmissions through these 
nerves, and how nicely adjusted must all the parts of this 
complicated apparatus be, that each may perform its office 
without interference with the rest! 

248. I have already alluded incidentally to the fact, that one 
nerve may be paralyzed, and others distributed to the same 
parts may be entirely unaffected. Thus the nerve of expression 
in the face may be paralyzed alone, the face retaining its usual 
sensibility and its power of performing other motions than those 
of expression, as mastication, because the nerves of common 
sensation and of common motion are untouched by the disease. 
So, too, in the nerves which go out from the spinal marrow, 
composed of tubuli of motion and sensation mingled together, 
one set of the tubuli may be affected while the other is not; 
for in paralysis it is often the case that the sensibility remains 
while the power of motion is gone, and vice versa. Sir Charles 
Bell relates an interesting case, in which the paralysis was 
different on the two sides of the body. A mother was seized 
with a paralysis, in which there was a loss of muscular power 





THE NERVOUS SYSTEM. 


159 


Nerves, though having different offices, nil alike in structure. 

on one side, and a loss of sensibility on the other. She could 
hold her child with the arm of the side which retained its 
power of motion but had lost its sensibility. But she could do 
it only when she was looking at it. She could not feel her 
child on the arm, and therefore when her attention was drawn 
to any thing else, and she ceased to have her eyes fixed on the 
child, the muscles having no overseer, as we may say, to keep 
them at work, were relaxed at once, and the child would fall 
from her arm. In this case, bound up in the same sheaths were 
two sets of tubuli, one set of which were useless in the nerves 
on one side of the body, and the other set were useless in the 
nerves of the other side. 

249. We should suppose that there would be a difference in 
the construction of the nerves, corresponding with the different 
uses to which they are devoted. But it is not so. The micro¬ 
scope shows us that the nerves of motion and of common and 
special sensation are all alike in their structure, and chemistry 
shows us that they are alike also in their composition. The 
question arises, then, why the impression producing motion can 
not be transmitted by the same nerve with the impression 
causing sensation. The reason is evidently not to be found in 
the nervous trunk itself, as this is the same in all cases. It is 
in the circumstances of the two ends of the nerve—that which 
is in the nervous centre from whence it arises, and that which 
is expanded in some part of the body. You can see at once 
that the nervous tubuli which end in the fibres of a muscle 
can not transmit sensation to the brain from the skin over the 
muscle, because they do not go to the skin at all. There are 
other tubuli that are distributed there for that purpose, mingled 
indeed in most cases with the tubuli for motion, but yet kept 
entirely distinct from them. And besides, there is probably 
something in the mode of arrangement of the extremities of a 
nerve of sensation, which differs from that which exists in the 
distribution of a nerve of motion, so as to make it impossible 
for a nerve of motion to receive the impression producing sen¬ 
sation, even where the impression is made directly upon the 
muscle itself. There is also probably a different ending of the 
nerves of sensation and motion in the nervous centre, the brain, 
or spinal marrow, that makes the one kind incapable of 
performing the duties of the other kind. 

250. There have been many hypotheses in regard to the 
action of the nerves. The most common theory, even up to 
modern times, was this—that the brain is not only the great 






160 


HUMAN PHYSIOLOGY. 


Nerve-force not electricity. Proved by facts and experiments. 

centre of the nervous system, but its central workshop, as we 
may express it, and that in it is secreted a nervous fluid, which 
is distributed through all the body by the nerves, they being, 
as it was supposed, bundles of conduit-pipes. This fluid was 
supposed to move back and forth in the nerves, going outwards 
towards the extremities of the nerves to excite motion, and 
going inward to the brain to convey the sensation of external 
impressions. This theory has been exploded by the researches 
of Sir Charles Bell and others, and during the last half century 
important and numerous discoveries have been made, in rela¬ 
tion to the functions of different parts of the nervous apparatus. 
And though there are many things in this system, which links 
the spiritual with the physical, that we shall never understand, 
the bounds of our knowledge in regard to it are undoubtedly 
to be largely widened by future researches. 

251. It is a favorite idea with some physiologists that nerve- 
force, as it is termed, is identical with electricity, and that the 
nervous system is therefore a system of electrical batteries, with 
an apparatus for a sort of telegraphic communications. They 
ground their opinion upon the fact, that a current of electricity 
passed along nerves may produce motion or sensation, accord¬ 
ing to the character of the nerve through which it is passed, 
and also upon the analogy which exists between nerve-force 
and electricity in the instantaneousness of their transmission. 
But facts and experiments have wholly disproved this alleged 
identity. Some of these I will briefly relate. Mechanical and 
chemical stimuli produce the same nervous action that elec¬ 
tricity does. This shows that the electricity acts merely as a 
stimulus to wake up the nerve-force, instead of being that force 
itself. Experiments have been tried, to detect, if possible, the 
existence of an electrical current in a nervous trunk while the 
parts to which it is distributed were in action, but in vain. 
Thus, Prof. Matteucci laid bare the large nerve of the leg of a 
horse, and although by irritating its roots he excited powerful 
action of the muscles of the leg, the instrument in connection 
with the nerve was entirely unaffected, though it was so ex¬ 
tremely delicate that it would indicate an infinitesimally small 
disturbance of the electrical equilibrium. Again, a ligature put 
around a nerve will by its compression prevent nervous trans¬ 
mission through it, but will not hinder the passage of an elec¬ 
trical current. Still again, if a piece of a nerve be cut out, and 
some good conducting substance be introduced in its place,, 
electricity will pass, but there can be no transmission of nerve 





THE NERVOUS SYSTEM. 


161 


Products of nervous action—sensation, motion voluntary and involuntary. 

force to the parts below the division. Besides all this, nerve- 
force differs from electricity in the fact that it can be confined 
to the nervous trunk, or even to a small portion of the trunk, as 
when a motion is very limited in extent; while electricity not 
only passes through the whole trunk, to all the parts to which 
the nerve is distributed, but is diffused in the parts around it. 
Thus, if an electrical current be passed through the main nerve 
of the limb of an animal, it will go through every branch 
of that nerve, and cause all the muscles of the limb to contract; 
but nerve-force may be so insulated in a small portion of the 
nerve, that a single toe may be moved alone. And some of the 
electricity will be diffused at once in the muscles and other 
parts around the trunk of the nerve before it reaches any of the 
branches that go off from it. Indeed, the muscles are much 
better conductors of electricity than the nerves, which should 
not be if the nerves were particularly designed for its transmis¬ 
sion, as the hypothesis would claim. And both muscles and 
nerves are nothing like as good conductors as a common copper 
wire. 

252. We have thus far contemplated nervous action, for 
the most part, only in two forms—as producing sensation 
and voluntary motion. In sensation the action is from the 
extremity of the nerve to the nervous centre; but in motion it 
is from the centre to the extremities of the nerves, as they are 
expanded among the fibres of the muscles. This voluntary 
motion, you see, may arise in consequence of sensation, as 
when you withdraw the hand from the fire, if the heat be 
painful; or it may occur without a preceding sensation, as 
when the thinking mind wills to perform certain motions for 
effecting some purpose. In either case it is supposed that the 
gray vesicular or cellular substance of the brain is in immediate 
connection with the mind, and that the white tubular matter 
of the brain and the nerves serves only for transmission. That 
is, both in sensation and motion the effective physical agency is 
in the vesicular gray substance. This is the working part of 
the telegraphic apparatus of‘the mind, while the innumerable 
tubuli of the white matter of the brain and nerves are the 
communicating wires. 

253. Much of the muscular motion of the body is produced 
without the agency of the will, and sometimes even in oppo¬ 
sition to it. This is true of the motions caused by emotions in 
the mind. For example, the muscular motions in sobbing and 
in .aughing often occur in opposition to the strong action of the 





162 


HUMAN PHYSIOLOGY. 


Involuntary motion. Excitor and motor nerves. 

will. In this case, the emotion produces its effect upon the gray 
vesicular substance, and from this the impression is transmitted 
through the nerves to the muscles. 

254. There are some common motions which are performed 
to a greater or less extent without the agency of the will. The 
muscles which perform them are called involuntary muscles. 
The muscles of respiration, for example, ordinarily act without 
our willing them to do so. If they did not, respiration would 
stop when we sleep, or become stopped from disease. But the 
will can quicken these muscles in their action. They are 
therefore not wholly involuntary. But there are some purely 
involuntary muscles. The muscular coat of the stomach, which 
I spoke of in the Chapter on Digestion, as being constantly in 
motion when the stomach is filled with food, is of this char¬ 
acter. No effort of the will can quicken or retard the action of 
this muscle. That exceedingly compound muscular engine, 
the heart, is a collection or arrangement of purely involuntary 
muscles. No effort of the will can directly influence its 
motions, though it may do it indirectly, by so directing the 
thoughts as to awaken emotions calculated to produce this 
effect. That beautiful circular curtain in the eye, the iris, has 
the size of its circular opening, the pupil, controlled, as you will 
see in the Chapter on the Eye, by an involuntary muscle. 

By what agency, you will inquire, ’are these involuntary 
motions produced ? The answer to this question will open to 
you a new view of the nervous system. 

255. I have already alluded to the two roots which unite to 
make up each nerve that comes from the spine. One of these 
roots is composed of tubuli through which impressions are 
transmitted to the spinal marrow; and the other contains 
tubuli, through which an impression is transmitted from the 
spinal marrow to the muscles, causing them to contract. Each 
nerve, then, coming from the spine, is made up of two distinct 
nerves, or two distinct sets of tubuli. One of these is called an 
excitor nerve, the other a motor nerve. In the case of the 
muscles of respiration, every time that they act, the process is 
this—an impression is transmitted from the lungs through an 
excitor nerve to the spinal marrow, the gray vesicular substance 
there responds to this impression, and sends in consequence an 
impression by a motor nerve to the muscles. So in the case 
of the iris, which contracts to prevent too much light from 
entering the eye, the light as it strikes the retina produces an 
impression, which is transmitted through an excitor nerve, and 




THE NERVOUS SYSTEM. 


163 


Reflex action of nerves. Sometimes sensation with it, and sometimes not. 

in consequence another impression is transmitted through a 
motor nerve to the iris. So also, the presence of food in the 
stomach produces an impression ■which is transmitted through 
the excitor nerve, and another impression is returned through 
the motor nerve, excitino* the muscular coat to action. And in 
the act of swallowing an impression is transmitted from the 
food thrust back into the throat, and then impressions are 
returned to the many muscles engaged in this compound act, 
(§ 78). The action of the nerves illustrated by these examples 
is termed their reflex action, because the impression transmitted 
by one nerve to the spinal marrow is reflected from it by 
another. 

256. You see that I use the rather indefinite word, impres¬ 
sion , in relation to the transmissions through the nerves. It is 
the best word that can be employed, because although some¬ 
thing is transmitted, we know not what that something is. 
The result of the transmission is different in the excitor nerve 
from what it is in the motor nerve. The result differs also in 
the excitor nerves according to circumstances. In some cases 
it is accompanied with actual sensation, while in others it is 
not. That is, the brain sometimes participates in the result, 
and sometimes it is confined to the spinal marrow. Thus, in 
the act of respiration, the impression carried from the lungs by 
the excitor nerves comes from the presence of dark blood in the 
lungs. Ordinarily, a mere impression, and nothing like sen¬ 
sation, is transmitted. The respiratory muscles, most of the 
time, go on to do their work, in obedience to the impres¬ 
sions communicated from the lungs, without the process being 
recognized by the mind. But when there is embarrassment 
in the lungs,* the quiet process, carried on through the ageucy 
of the spinal marrow alone, is not adequate to meet the exi¬ 
gency. In some way, the brain becomes a party in the ope¬ 
ration. The act of breathing is now accompanied with pos¬ 
itive sensations, and there is a mixture of voluntary and 
involuntary muscular action. So, also, the ordinary movements 
of the stomach are attended with no positive sensations. That 
is, there is no transmission to the brain of any impression of 
which the mind takes cognizance. But if there be disturbance 
there, and extraordinary movements are produced, then cogni¬ 
zance is taken of them, and sensations of various kinds result. 

257. The spinal marrow, in relation to the involuntary 
muscles, seems ordinarily to be in a great measure independent 
of the brain ; while on the other hand, in relation to voluntary 




164 


HUMAN PHYSIOLOGY. 


The spinal marrow performs two separnte functions. 

motion and sensation, it forms the chain of communication be¬ 
tween the brain and the moving and sentient parts. In this 
respect the dependence is perfect. In injuries of the spine, 
therefore, the extent of the loss of the power of motion and of 
sensibility depends on the nearness of the injury to the brain. 
The higher up the injury is, the larger is the number of nerves 
whose connection with the brain is cut off, and therefore the 
greater is the extent of body rendered insensible and motionless. 

258. The spinal marrow then performs two separate functions 
■—one, in producing involuntary motion, as an organ by itself; 
and another, as an organ in connection with the brain, in the 
production of voluntary motion and sensation. The arrange¬ 
ment, by which it does two things which are so different from 
each other, will be clear to you, if you bear in mind the fact 
that the spinal marrow, like the brain, is composed of the two 
nervous substances, the white tubular, and the gray vesicular sub¬ 
stance. When the spinal marrow acts as a mere medium of 
communication for the brain, the transmission is made directly 
through the tubes of the white substance to and from the brain 
—to the brain in sensation, and from, it in voluntary motion. 
Thus, when a sensation is felt in the foot, the impression made 
there is transmitted through the nerve to the spinal marrow, 
and up through the white part of this organ to the brain. It 
touches none of the gray substance of the spinal marrow, but 
goes to the gray substance of the brain. And when the foot is 
moved, an impression is returned from the brain through the 
white part of the spinal marrow, and then through the nerve 
which goes from it to the muscles that move the foot. But, on 
the other hand, when the spinal marrow acts by itself, inde¬ 
pendently of the brain, producing what is called reflex action, 
(§ 255,) the impressions that are transmitted, some of them 
begin, and some end in the gray substance of the spinal 
marrow. The impression on an excitor nerve ends there, and 
the impression on a motor nerve begins there, the latter result¬ 
ing from the former, except’ when motion is produced by dis¬ 
ease in the sp:nal marrow itself. Thus, in breathing, as de¬ 
scribed in § 255, an impression goes from the lungs through 
excitor nerves to the gray substance, and that is the end of it; 
but another impression begins there as a result of it, and is 
transmitted to the involuntary muscles moving the chest. 

259. One marked distinction between the brain and spinal 
marrow is, that the brain has its intervals of rest; but the 
''unctions of the spinal marrow never cease for a moment as 




THE NERVOUS SYSTEM. 


165 


The brain rests. The spinal marrow does not. Convulsions. 

long as life continues. In sleep the brain is more or less at 
rest, and it is in a state of entire torpor when the sleep is pro¬ 
found. But during sleep the heart beats, the respiratory- 
muscles work the chest, and the muscular coat of the stomach 
churns the food if there be any there. For these motions, with 
many others, are dependent upon the spinal marrow, and not 
upon the brain; and so, while the brain sleeps, the spinal 
marrow keeps up the operations of the system that are essential 
to the continuance of life, in the manner described in § 255. 
So, also, in apoplexy, when the brain is torpid from the 
pressure of blood, the spinal marrow, being unaffected, keeps up 
the functions of those organs which are dependent upon it. 
But besides the motions that I have mentioned, as being kept 
up by the spinal marrow, when the brain is torpid from any 
cause, there are other motions which can be excited by stimu¬ 
lating nerves that are connected with the spine. For example, 
the act of swallowing can be produced by pouring a liquid into 
the mouth, and motion can be produced in the muscles of a 
limb by irritating the limb at different points. If you cut off 
the head of a frog, and thus destroy all sensibility, you can 
produce movements in his limbs by irritating them. You 
can, indeed, make the whole body to move together, by 
producing irritation at many points at the same time. So, too, 
if a man be paralyzed in his lower limbs by a blow upon 
the spinal column, these parts, which he cannot move b}^ his 
will, can be excited to motion by irritation with electricity 
or other agents. 

260. The motions of the muscles in convulsions are pro¬ 
duced by the agency of the spinal marrow. The irritation 
causing them sometimes exists in the spinal marrow itself, 
being the result of disease there. But commonly the irritation 
is in some other part of the system, and it produces the con¬ 
vulsive movements by sending an impression through excitor 
nerves to the spinal marrow, to be reflected back through the 
motor nerves, as described in § 255. The brain during the 
convulsion is in a torpid state, the individual being uncon¬ 
scious. That the brain is involved to some extent in the con¬ 
vulsion is very clear, and sometimes the cause of the convul¬ 
sion is in this organ. But it is probable that the convulsive 
movements are directly dependent on the spinal marrow, and 
that even when the cause is in the brain, it is by the action of 
the spinal marrow, sympathizing with and affected by the 
diseased brain, that the convulsion is produced. And when 




166 


HUMAN PHYSIOLOGY. 


Involuntary action of voluntary muscles. How produced. 

the cause is in some other part, as in the irritation of teething 
or indigestion, the impression is sent directly to the spinal 
marrow, and is reflected from it to the muscles, the brain being 
only secondarily affected. 

261. It is worthy of remark, that in convulsions there is a 
purely involuntary action of muscles, that are ordinarily under 
the control of the will. How is this ? How are they taken 
away from the usual control of the will so suddenly and so 
entirely ? It is not possible that any temporary new connec¬ 
tions can be established all at once by the disease,—that there 
is, to use illustrations of a familiar character, a sort of unship¬ 
ping of the usual connection, and a hitching on of another for 
the time being, or a switching off from one track on to 
another. These voluntary muscles must have all the time a 
connection with the gray substance of the spinal marrow, just 
as the involuntary muscles have, only it is not as intimate and 
extensive. If it were not so, they could not act occasionally as 
involuntary muscles. Being thus connected with the gray 
substance, both in the brain and spinal marrow, when they 
act in obedience to the will, the impression exciting their ac¬ 
tion comes to them from the gray substance in the brain 
through the white part of the spinal marrow; but when they 
act involuntarily, the impression comes from the gray sub¬ 
stance in the spinal marrow, and not from the brain. 

262. I may remark farther, that the voluntary muscles act 
involuntarily more often than is commonly supposed. As 
already stated, (§ 259) in animals, from which the head has 
been removed, the voluntary muscles can be excited to involun¬ 
tary action, resembling voluntary movements, although of 
course with the removal of the head were destroyed all sensa¬ 
tion and all exercise of the will. And in the case of the man 
paralyzed by injury in the back, alluded to also in § 259, in¬ 
voluntary movements can be excited in the voluntary muscles. 
A pigeon, whose cerebrum had been removed, would fly when 
thrown into the air, would run when it was pushed, and would 
drink when its beak was put into water. There was no sensi¬ 
bility and no will in this case, for they can not be without the 
cerebrum. The movements were involuntary, though per¬ 
formed by voluntary muscles. Now as these facts prove that 
voluntary muscles are, through their connection with the spinal 
marrow, capable of acting as involuntary muscles also, the 
question arises, whether they do not much of the time act in 
part as involuntary muscles, and sometimes wholly so. That 





THE NERVOUS SYSTEM. 


167 


Walking. Reverie. Brain not directly essential to life. 


this is the case, a little reflection will show. When we are 
walking we use voluntary muscles. But manifestly a distinct 
act of the will is not put forth for every motion performed 
in walking. The mind may be at the same time fixed upon 
something else ; and there seems ordinarily to be only an oc¬ 
casional action of the will, as when we change our course, or 
when some obstacle is in the way, requiring a variation from 
the regular consecutive series of movements. There is a dis¬ 
tinct action of the will when the movements begin ; but after 
this the motions seem for the most part almost automatic, and 
are probably produced by the reflex action of the spinal mar¬ 
row, the will interfering only when occasion requires. This is 
more manifestly the case when one is walking in a reverie, and 
perhaps finds himself on awaking from it, in a different place 
from that to which he had willed to go. It is as if the brain 
set the machinery of the limbs to work, and then delivered it 
over’to the care of the spinal marrow, interfering only when it 
needs to do so to meet some difficulty, or when it wishes to 
give a new direction to the movement, or to stop it. And in 
a reverie, the brain occupied with other things, neglects even 
to exercise this superintendence, and leaves the machinery 
wholly to the guidance of the spinal marrow. The same re¬ 
marks can be made in regard to other motions, as in speaking, 
singing, playing on an instrument, &c. In all these cases the 
voluntary muscles act in some measure involuntarily, being 
governed by an association in their action which is far from 
being wholly dependent upon the brain, and the direction of 
the will. I shall recur to this point again, when I come to 
treat of the connection between the mind and the body. 

263 . Many experiments have been tried upon animals in 
reference to the functions of the brain, and of the spinal mar¬ 
row. I have already alluded to some of them. It was 
formerly supposed, that the brain was the only centre of nerv¬ 
ous power, and that it was immediately essential to the pre¬ 
servation of life. But these experiments have shown that this 
is far from being the truth. The brain, it has been found, has 
nothing to do directly with the maintenance of life. Animals 
live for some time after the brain is destroyed. A pigeon was 
kept alive for some months after its cerebrum was removed. 
Its condition was very much like that of a man, the functions 
of whose cerebrum are suspended by the pressure of a frac¬ 
tured portion of the skull. Although, like him, the animal 
had lost all sensation and voluntary motion, yet, like him, it 




168 


HUMAN PHYSIOLOGY. 


Upper part of the spinal cord directly essential to life. 


continued to breathe, and its heart continued to beat. Of 
course so extensive an injury of so important an organ will at 
length cause death; but life continues long enough in such 
cases to show, that this organ is not immediately essential to 
its continuance. The functions most essential to life, the 
respiration and circulation, are, as you have seen, kept up by 
the spinal marrow. The very upper part of this organ is espe¬ 
cially devoted to this purpose. You may take out the brain 
of an animal, and destroy all its spinal marrow, except this 
upper portion of it, and the animal will still breathe, and its 
heart will beat. But if you destroy just this small portion of 
the spinal marrow, though you leave the rest of it and the 
brain untouched, the animal will die at once from the cessa¬ 
tion of the respiration and the circulation. In the Spanish 
bull-fight, when the matadore at length kills the animal, by 
adroitly piercing the spine in the back of the neck, he inflicts 
his wound upon this upper part of the spinal marrow. 

264. If after cutting off the head of a frog, you divide the 
spinal marrow in the back, you can produce involuntary mo¬ 
tions in both the upper and lower extremities. But you can not 
produce them at the same time in both together, for the divi¬ 
sion of the spinal marrow in the back separates it into two 
independent parts. When, therefore, you irritate the upper 
extremities, the motion is confined to them, and the lower ex¬ 
tremities are quiescent. And if you irritate the lower extrem¬ 
ities, the motion produced there does not extend to the upper. 
The division can be carried much farther with similar results. 
If the spinal marrow be divided above and below where a pair 
of nerves is given off, so as to separate this point wholly from 
the rest of the nervous system, the reflex action can be excited 
in the nerves connected with this point. That is, an irritation 
of the parts supplied by the excitor nerve of this little segment 
of the spinal marrow will produce an impression in that seg¬ 
ment, which will be reflected by the motor nerve to the 
muscles. The gray substance of the spinal marrow may, there¬ 
fore, be regarded as a chain of little brains, in some measure 
separate from each other. But while there are thus many 
centres of reflex action, there is only one centre of sensation 
and voluntary motion, and that centre, the brain, is connected 
with the mind. Some physiologists have maintained that 
there is sensation independent of the brain; but it may bo 
considered as most abundantly proved, that it is through the 
brain alone that the mind feels and acts, or rather that we 




THE NERVOUS SYSTEM. 


169 


Two systems of nerves, cereoro-spinal and sympathetic. 

know nothing in this world of a sentient and acting mind 
existing without a brain. 

265. The system of nerves which we have been examining 
is termed the cerebrospinal, from its two great central organs, 
the brain and spinal marrow. But there is another nervous 
system, the functions of which are involved in much mystery. 
It is called the system of the great sympathetic, or the sympa¬ 
thetic system. Sometimes it is called the nervous system of 
organic life, because it is so intimately and extensively con¬ 
nected with the nutritive processes ; while the system that we 
have been considering is called the nervous system of animal 
life, because it regulates the functions peculiar to animals in 
distinction from plants, sensation, and spontaneous motion. 
While the sympathetic system is thus connected- with the 
nutritive processes, it is also supposed to be the means of effect¬ 
ing the sympathetic connection between different parts of the 
body, and to act as the medium by which the passions and 
emotions of the mind produce their effects upon the functions 
of the different organs. In this system there are many gang¬ 
lions or little brains, which communicate with each other by 
nerves. There is a chain of them along in front of the spinal 
column, and there are two quite large ones in the abdomen. 
This system has connections everywhere with the cerebro-spinal. 
The purposes aimed at in the particular arrangements of this 
system are as yet but little understood, and we probably never 
shall know as much about it as we shall about the cerebro¬ 
spinal system. The arrangement of the sympathetic system 
differs very materially from the cerebro-spinal. It is a single 
system, and has no symmetrical arrangement, while the 
cerebro-spinal has throughout two halves which are precisely 
alike. 

I have thus described the arrangements and functions of the 
nervous system to such an extent, as will prepare you for the 
consideration of those subordinate organs, by which the pur¬ 
poses of this system are accomplished. After treating of the 
organs of locomotion, the voice, and the senses, I shall call your 
attention again to this system, presenting some views of ’ts 
uses and connections, which you will then be better prepared 
to understand. 


15 




170 


HUMAN PHYSIOLOGY. 


Rones the framework of the body. Composition of bone. 


CHAPTER II 

THE BONES. 

260. The bones furnish the points of support and attach¬ 
ment for the muscles which move the different parts of the 
body. They are, therefore, the passive instruments of loco¬ 
motion. I treat of the bones before the muscles, because you 
will then better understand the action and the arrangement 
of the muscles. 

267. The bones, forming the framework of the body, not 
only furnish points of support and attachment to the muscles, 
but in many cases serve to defend important organs from in¬ 
jury. Thus, the soft brain is thoroughly secured from harm 
by being inclosed in the skull; and the lungs are surrounded 
by walls of bone so arranged, as you saw in the chapter on 
Respiration, that, while they defend the lungs from external 
violence, they secure a wide range of motion for the necessary 
expansion of these organs. 

268. The bones are composed of two parts, the earthy or 
hard portion, and the animal portion which is soft. Each of 
these portions, as was stated in § 60, can be obtained separate 
from the other. These two portions of bone exist in different 
relative proportions in the different periods of life. In the 
child the animal portion predominates, while the mineral 
does in old age. It is a wise provision in regard to the 
child, for if his bones were as brittle as those of old age, 
or even as those of middle life, they would be often broken 
in the falls to which the child in its feebleness and carelessness 
is subjected. 

269. There are some points of interest in relation to the 
structure of bone and its growth. I stated in § 61 that bone is 
generally formed in cartilage, the cartilage being formed first as 
a mould for the bone. Bone is deposited in two forms, solid and 
cellular. In the flat bones, as in the skull, the cellular struc¬ 
ture lies between two plates of solid bone. In the long bones 
the cellular part is at the two ends, and is covered with a 
thin plate of solid bone, while the shaft is a hollow tube 
with the bone very much condensed. This arrangement 




THE BONES. 


171 


Structure of bone. Long bones hollow. Marrow. 

is seen in Fig. 83, representing 
the thigh-bone and the bone of the fig. 83. 

arm. Certain well known mechanical 
principles are observed in this arrange¬ 
ment. The bone would be unneces¬ 
sarily heavy if it were solid through¬ 
out. Lightness in a moving limb is 
of considerable importance. At the 
same time strength is to be carefully 
provided for in a bone which is to 
sustain the weight of the body, and 
to which the large muscles of the 
thigh are attached. By having the 
bone hollow, both of these objects, 
lightness and firmness, are secured. 

The principles involved are recognized 
by the architect in the construction 
of pillars, and we see tljem exemplified 
in the hollow stalks of plants. The 
hollow pillar has more strength than 
the same ‘quantity of matter would 
have if in one compact mass; and 
the stalk which supports the full clus¬ 
ters of grain, would break under its 
load as it moves back and forth in 
the wind, if it were solid instead of 
being hollow. But the round cavity 
of the shaft of the bone does not 
extend to the ends. These are ne¬ 
cessarily large, in order to present broad surfaces for articu¬ 
lation with the neighboring bones; and strength and light¬ 
ness are secured in this case by a cellular arrangement of the 
bony matter, the outer plate of solid bone being comparatively 
thin. There is obviously more firmness in the resistance to 
shocks or pressure, secured in this way, than there would be if 
the bony matter were all consolidated into a shell containing a 
cavity. 

270. The round canal in the shaft and the cellular structure 
at the ends are filled with an oily substance called marrow. 
This, like all other fatty substances, is contained in fat cells, as 
described in the chapter on Cell-Life. The marrow is also 
present in the cellular structure between the plates of the flat 
bones. The cavities and the cells in bones have branching 








172 


HUMAN PHYSIOLOGY. 


Mode of nutrition in bones. No bloodvessels in their solid parts. 


about in them bloodvessels, which are branches of arteries and 
veins that enter the body of the bone at some particular points, 
in the long ones near the middle of the shaft. It is from these 
bloodvessels, together with those that come from the mem¬ 
brane investing the bone, called periosteum, that the bone is 
nourished. But, although an artery runs through the body of 
the bone, to branch out upon the walls of its cavity, none of its 
branches enter the very substance of the bone. How then is 
the bone nourished, that is, constructed and kept in repair? 
The manner in which the material for this purpose is carried 
to every point of the solid bone has been developed by the aid 
of the microscope, and I will describe it to you. If we cut 
across the solid portion of a bone, and examine it with a 
microscope, we see here and there orifices of certain minute 
canals that run lengthwise of the bone. These canals are 
found to communicate with the cavity of the bone and receive 
therefore blood, or some of the constituents of the blood, from 
the bloodvessels which are situated there. These orifices, as 
seen under the microscope, are represented in Fig. 84. Around 
these orifices a a, you see little dark spots arranged in rings, 
with lines running to tb m from the orifices. By magnifying 
the section of bone still nore, we see what these spots and lines 
are. The dark spots are small cavities, and the lines are 
minute tubes running to them. In Fig. 85 is a representation 
of this arrangement as seen in a little portion of the section of 
bone, more highly magnified than it is in Fig. 84. The 


FIG. 84. 



SECTION OF BONE. 





THE BONES. 


173 


No sensibility in bones. Variety of shape. 


tubes pass out from the canals to the rows of cavities which 
are around the canals, and thus a circulation is kept up at 
every point of the solid bone. It is supposed that the blood 
itself does not circulate in these little channels and cavities 
in the solid bone, but a fluid containing the constituents of 
bone. For these channels are too small even to admit the 
cells which the microscope shows us as swimming in the blood. 
The fluid that circulates in them is selected from the blood, 
which is contained in the bloodvessels in the cavity of the 
bone, and in the periosteum that envelopes it. 

271. It is a very common popular notion, that the bones are 
endowed with great sensibility, and especially the central part, 
the marrow. The surgeon is very often asked if the sawing of 
the bone in amputation is not very painful, and if when the saw 
reaches the marrow it does not produce agony. But the 
bones have in their healthy state no perceptible sensibility, as 
I have before stated, and the sawing of the bone in amputation 
occasions no suffering. When, however, a bone becomes in¬ 
flamed, severe pain is one of the symptoms. And it is well 
that it is so; for if it were not, disease might go on to pro¬ 
duce disastrous results in a part so covered up by others, with¬ 
out any warning of the danger <5f the case. 

272. The bones are of every variety of shape, to suit the 
various offices which they are to fulfill. You will see this to be 
true, as you cast your eye over the skeleton as represented in 
Fig. 8G. You first observe the somewhat round box of bones, 
which contains the brain, and at the same time furnishes 
sockets for the eyes, extended irregular surfaces for the appara¬ 
tus of smelling, and for that of the taste, a place for the organs 
of hearing, and at its lower part, in connection with the lower 
jaw, a mill for grinding the food. Then you observe the many 
bones of the thorax or chest, containing and protecting the 
heart and the lungs. The spinal column , k, composed of 
twenty-four bones, you see as a firm but movable pillar, ex¬ 
tending the whole length of the body, and having its base 
firmly planted upon that stout thick bone, the sacrum , which 
is wedged in so tightly like the key-stone of an arch, between 
the broad spreading bones on either side. To this pillar are 
strongly fastened the walls of the chest; and from the chest 
thus supported by the spine hang the lax front and lateral 
walls of the abdomen. Then below you see the pelvis , as it is 
called,—a set of large bones so arranged in a bowl-form, as to 
offer a broad surface of support to the contents of the abdomen. 

15* 




174 


HUMAN PHYSIOLOGY, 

The bones of the skeleton. 



FIG. 86. 


SKELETON. 

















THE BONES. 


175 


Bones of the cranium and the face. 


The bone called the ilium, m and l, on either side, with its 
flaring upper surface, is especially serviceable in this way. 
The pelvis also furnishes a socket for the round head of the 
thigh bone s , and points of attachment for the large muscles 
that move the lower extremity. You observe the large bones 
of the thigh and leg, intended to give firmness to the lower 
extremity, and the lighter bones of the arm and forearm, fitted 
for extent and quickness of motion. And finally, you notice 
the numerous bones of which the hand and foot are made up, 
giving them with the intervening cartilaginous coatings, great 
elasticity, and vast variety of motion, especially in the hand. 

273. I will notice with some particularity some of the 
bones, of which I have given a general description, as they are 
united together to form the whole skeleton. I can not notice 
them all, nor dwell upon every point of interest, for this would 
require much more space than I can devote to the subject. I 
shall, therefore, select those points which can be made most 
clear and interesting. 

274. I first call your attention to the bones of the head, as 
you see them in Fig. 87. There are twenty-two bones in the 
whole head. Fourteen of these belong to the face, while eight 
belong to the cranium, that is that part of the skull which in¬ 
closes the brain. Of these, notice particularly the large bone 
in front called the frontal bone, a, making the forehead, and 
below forming the upper portion of the orbits of the eyes; 
the parietal bone, b, the upper lateral part of the dome of the 


FIG. 87. 



BONES OF THE HEAD. 








176 


HUMAN PHYSIOLOGY. 


Why so many bones in the skull. The two tables, and the sutures. 

skull; and c the temporal bone on which the parietal bone 
rests. There is a large bone in the rear forming the back of 
the cranium as the frontal bone does the front. There are 
also two bones in the base of the cranium which are out of 
sight in this view of the skull. You may, perhaps, be disposed 
to inquire why this box for holding the brain, should be made 
of so many bones. One reason is, that the enlargement of the 
skull from infancy to adult age is effected more easily and 
better than it would be if the cranium were one bone. Another 
reason is, that even in the adult, in whom these bones are at 
length so tightly united, violence is less apt to produce injury, 
from the giving, as it is expressed, of the bones upon each 
other, than it would be if one bone made the whole structure. 
And this is especially true of the child, in whom the bones are 
very imperfectly united. Hence it is that the frequent falls of 
children upon their heads so seldom do any injury. 

275. The principal bones of the head are composed of two 
solid plates, while the bony matter between these plates is ar¬ 
ranged in a cellular or sponge-like form. The outer table or 
plate (for both of these terms are used in relation to it) is 
rather rough, and in some parts has ridges for the attachment 
of muscles. But the inner plate is very smooth on account of 
the soft delicate organ that is contained in the cranium. It is 
so brittle that it has been called the vitreous table, from its re¬ 
semblance to glass in this respect. The modes of the joining 
of the bones differ in the two tables'. In the outer table tho 
joining is by a minute dovetailing, called a suture. Numerous 
little projections from one bone fit accurately into correspond¬ 
ing spaces in the edge of the other. This is very well repre¬ 
sented in Fig. 88, in which you see the sutures on the top of 
the skull; b being the suture which is formed between the 
two parietal bones; a a, that between the parietal and the 
frontal bone in front; and c c, that between the parietal and 
the bone which forms the back of the cranium. A better 
joining for bones of such a shape as these have can not be con¬ 
ceived of. But the inner table is joined differently. It is so 
brittle that the small projections of the dovetailing mode of 
joining would not answer here, for they would break very 
easily. The joining accordingly is in this case by smooth 
accurately fitted edges, somewhat beveled, so that one slightly 
overlaps the other. 

276. The upper part of the cranium is in the shape of a 
dome, and is constructed upon the same principles that such 




THE BONES. 


177 


The cranium a dome. Contrivances for giving it strength. 


FIG. 88. 


SUTURES IN THE SKULL. 



structures are in regard to resistance to pressure or violence. 
Just as in the domes that are built by man, so in this dome 
of the cranium, great strength is secured around the lower 
part, so as to resist outward lateral pressure. In the dome 
of St. Paul’s there is a double iron chain around its base 
for this purpose, of course concealed from view. In the head 
of man the dome may be considered as composed of the 
frontal bone in front, the parietal bones at the side, and the 
occipital bone in the rear. In front you see the base of 
the dome strongly fortified, in the heavy arches that form the 
upper part of the sockets of the eyes, and on the jutting edges 
of which are the eyebrows. In the rear the base of the occi¬ 
pital bone is very thick, and is fortified with ridges which 
furnish attachment to the large muscles in the back of the 
neck. But the most marked and interesting contrivance for the 
strengthening of the base of this dome is at the side. It is where 
the parietal bone 6, as seen in Fig. 87, is joined by the temporal, 
c. The joining here is not by suture, for that would afford no 
resistance to lateral pressure, either outward or inward. To 
secure this object, the lower bone, the temporal, laps over the 
upper, the parietal, with a beveled edge. It abuts upon or 
against it. It has the relation to the parietal of a buttress to 






178 


HUMAN PHYSIOLOGY. 


Defenses of the brain. Many and efficient. 

an arch. You can readily see that when great pressure is 
made on the top of the head, as when a heavy load is carried 
there, there must be a tendency to outward lateral pressure at 
the base of the dome of the cranium, and that this is effectually 
resisted by the temporal bones acting as buttresses. The same 
thing is true, also, when a blow is inflicted on the top of the 
head. And if a blow be received at the side of the head, on 
the temporal bone, it is evident that the bones will not be so 
apt to be fractured and pressed inward upon the brain, as they 
would be, if they were united by suture. 

27*7. You are now prepared to see, to what extent the brain 
is guarded against the effects of violence inflicted upon the 
head. These effects come either from fracture of the bones, 
or from concussion without fracture. In either case the vibra¬ 
tion of the parts concerned is the cause of these effects. The 
guards of the brain defend it from injury by lessening or dif¬ 
fusing this vibration. And it is to be observed, that when 
vibration passes from one texture to another, it loses some of 
its force in the change. No two substances vibrate just alike ; 
and when a vibration in one is communicated to another, it is 
modified, and is therefore lessened. Some substances modify 
and lessen vibrations communicated to them more than others 
do. If you apply these principles to the effects of violence on 
the head, you at once see that the brain would be much more 
apt to receive a dangerous shock from the vibration occasioned 
by a blow, if its coverings were condensed into one firm and 
thick layer of substance, than it is now. So also, if the bones of 
the head were in one solid layer, instead of having two layers, or 
plates, with the spongy structure between, and the integuments 
were all consolidated into one thick substance, there would be 
much more liability to fracture than there is with the present 
arrangement. Observe now how many, and how various are 
the textures, through which the vibration of a blow must pass, 
before it reaches the brain. Outside of the bone there is first 
the hair; next comes the skin; then there is the cellular mem¬ 
brane containing some fat; then a muscular coat; and lastly, 
the lining membrane over the surface of the bone. These 
various textures must deaden very much the force of a blow, 
and especially the outer cushion of hair, and those inner 
cushions, as we may call them, of fatty cellular membrane and 
of muscle. Then, when the vibration reaches the bone, it is 
lessened by the two plates with the intervening cells, and 
there is diffused largely among the many bones that unite with 




THE BONES. 


179 


Skull especially guarded at some poiuts. 

the one on which the force comes. Then as the shock goes 
into the brain, it is still farther lessened by the membranes 
which cover that organ. These greatly diminish the vibration, 
precisely as a coating of leather on the inside of a bell would 
deaden its vibration when produced by a blow upon the out 
side. With all these provisions the result is, that comparative¬ 
ly few of the blows received by the head do harm. The skull 
may be considered as a sort of helmet for the brain, its effect¬ 
iveness as a defense being very much increased by its cover¬ 
ings and linings. 

278. There are some especial guards at particular points in 
the cranium, where there is much liability to exposure to 
violence. Thus, as the lower part of the frontal bone, where 
the eyebrows are, is especially exposed, the distance from the 
surface to the brain is made considerable by an intervening 
chamber in the bone, called the frontal sinus. This sinus, 
which varies much in size in different individuals, is lined with 
a membrane, and communicates with the nose. You can see 
that this arrangement is a great protection to the bone at that 
point. The outer plate could be broken, while the inner is not 
injured. But the protection which this arrangement affords, 
is not confined to that single point; it serves also to deaden 
the vibration of a blow received by any part of the forehead, 
or by the forehead as a whole. The side of the head, too, is 
peculiarly exposed to blows. And, therefore, the skull is 
peculiarly guarded at this point. Beside the overlapping of 
the temporal bone upon the parietal, to which I have before 
alluded, the parietal bone is made thicker at its lower part, 
where it is most liable to be struck, than it is in most of the 
other parts of it. Then, too, the place of joining of the 
temporal and parietal bones is covered over by a thick muscle, 
the contractions of which you can feel if you press your 
fingers upon the temple while moving the lower jaw as in eat¬ 
ing. This cushion of muscle is of great use in breaking the 
force of a blow received in that quarter. Other points might 
be specified where there is arrangement for special protection, 
but those to which I have alluded will suffice. 

279. The cranium not only contains and protects the brain, 
but it at the same time serves various other purposes, and pro¬ 
tects other important organs. The tender and delicate eye has 
there a bony socket with jutting prominences all around it, to 
guard it against violence. The exceedingly minute and com¬ 
plicated apparatus of the hearing is also carefully protected by 




180 


HUMAN" PHYSIOLOGY. 


Complicated and extensive cavities in the nose. 

the skull, and the most important part of it is furnished with 
winding and intricate apartments, halls of audience, in that part 
of the temporal bone which is so hard, that it is called the 
petrous or rock-like bone. To the bones of the cranium are 
attached in various ways, the fourteen bones of the face. All 
these, with the exception of the lower jaw, are immovable. 
The two principal of them are the upper jaw bone, and the 
cheek bone. The former makes with its mate of the other 
side the forward portion of the roof of the mouth, the palate 
bones making its rear portion; and it furnishes the sockets for 
the teeth. It also at its upper part makes nearly the whole of 
the floor of the orbit of the eye. The cheek-bone forms the 
outer lateral part of the socket of the eye, and sending back a 
process or projection to unite with one from the temporal bone, 
c, Fig. 87, forms the zygoma or arch, inside of which the tempo¬ 
ral muscle passes down to be fastened to the lower jaw. The 
bones of the nose make quite a complicated series of cavities, 
for the purpose of presenting, in the mucous membrane, which 
lines them, a large surface, over which the nerve of smell is 
expanded. A representation of these cavities is given in Fig. 
89 ; in which a is the mouth ; 

6, the opening into the nos¬ 
tril ; d, a part of the base of 
the skull; c, the communica¬ 
tion of the nostril with the 
back of the throat; e, the cur¬ 
tain of the palate; l, the front¬ 
al sinus ; m, another large si¬ 
nus ; g , i, h , spongy bones pro¬ 
jecting into the cavity of the 
nostril. There is a large sinus, 
that is not seen in this figure, 
which lies over the teeth in 
the jaw-bone. The different 
sinuses are lined with the mu¬ 
cous membrane extending into them from the nose. These, with 
the spongy bones make a very large extent of surface in the 
cavities devoted to the sense of smell. The branches of the 
nerves of smell enter these cavities, to be distributed over 
thin walls, through many small openings in a bone in the 
»-oof of the nose, giving it a sieve-like appearance. 

280. The lower jaw is a bone shaped something like ahorse 
shoe, with its ends turned considerably upward. It has two 


FIG. S9. 

m g l i 



e a 

INNER BONES OF THE NOSE. 





THE BONES. 


181 


Structure of teeth. Three different kinds of texture. 


smooth projecting surfaces which articulate with two corres¬ 
ponding shallow cavities in the temporal bone. Its prominence 
at the lower part in front, the chin, is peculiar to man, there 
being no such prominence in any other animal. The lower 
jaw has sockets for the teeth, and it is so constructed, and is 
so arranged with muscles, that these teeth can be brought to 
bear against the teeth of the upper jaw in cutting and grind¬ 
ing motions. 

281. The teeth are very nearly like the bones in their 
structure, but they differ from them in some particulars which 
it will be interesting to notice. Every tooth has in it three dis¬ 
tinct structures, which differ in hardness, for reasons which will 
appear clear to you as I proceed. The dentine or ivory consti 
tutes the body both of the tooth and of its fangs. In the body 
of the tooth there is a coating of that very hard substance, the 
enamel, over the whole surface of the ivory. This is thickest 
over the top of the tooth, and grows thinner on the sides till 
it is entirely gone where the gum begins. The ivory in the 
fangs has a coating of a very different character, called the 
cementum. It is not hard like the enamel. This arrangement 
is represented in Fig. 90. This is a tooth with two fangs or 
roots; 1, is the enamel; 3, the den¬ 
tine or ivory: 2, and 7, the cement- 
um ; 4, an unnatural enlargement of 
the cementum, making an excres¬ 
cence ; 5, the cavity of the tooth 
supplied with bloodvessels and nerves 
which come through the channels 
that you see running up the middle 
of each fang. This cavity is analo¬ 
gous to that which is found in the 
shafts of the long bones as seen in 
Fig. 83. The ivory and the cement¬ 
um are seen by the microscope to be 
very different textures. The ivory 
is traversed by innumerable branch¬ 
ing tubes running from within out¬ 
ward towards the cementum, as 
represented in Fig. 91. This is a 
section of a small portion of the 
dentine and cementum in the fang of a tooth, very much mag¬ 
nified, cr, a, btmg the dentine, and c, c, the cementum, evidently 
a different structure. The structure of tbe enamel as exhibited 

16 


FIG. 90. 



Vertical 

SECTION OF A TOOTH. 





182 


HUMAN PHYSIOLOGY. 


How teeth are different from bones,,and why. 


FIG. 91. 



by the microscope is represented in Fig. 66 and 67, in the 
chapter on Cell-Life. I have been thus particular in the 
description of the parts of a tooth, that you may see how 
compound even so apparently simple a part of the body is. 
The three different structures in it are built by cells, and the 
cells of each part select from the blood such constituents as 
are needed for their purpose. 

282. A tooth differs from a common bone in one import¬ 
ant particular—when once formed it is never altered in its 
size. A bone grows with the growth of other parts of the 
body; but a tooth, when it first protrudes through the gum is 
as large as it ever will be. The reason of this is, that so 
hard a substance as enamel can not be made changeable as 
bone is. Its hardness is inconsistent with any thing like cir¬ 
culation in it, and without circulation there can be no change. 
If the enamel were not needed, and the teeth could be com¬ 
posed only of dentine, they could grow as other bones do. 
And if they could grow, one set of teeth might be made to 
answer the purpose. As it is, the second set are needed, be¬ 
cause as the jaws grow, the first set are neither large enough in 
proportion to the size of the jaws, nor numerous enough to 
fill up the whole space. If the first set were to be the only 
set, when the jaws became of their full size, the teeth would be 
altogether too small, and would be quite separated from each 
other. Twenty small teeth (the number of the first set) in the 
jaws of an adult, in place of the thirty-two large teeth of the 
second set, would present a very odd appearance, besides being 
incapable of doing the service required of them. 



















THE BONES 


183 


Hyoid bone. Patella. Spinal column. Its firmness and flexibility. 

Under the lower jaw is a little bone, called from its resem¬ 
blance to the Greek letter v, the hyoid or u-like bone. Its 
round end is towards the root of the tongue, and its two ends 
reach backward towards the spine. The larynx is suspended 
from it as from a frame, and the muscles that draw up this 
bone, draw up the larynx with it. It is one of the few bones 
in the body that are not directly connected with any other 
bone. The patella , or kneepan, is one of these bones. The 
four little bones in the ear, of which I shall speak particularly 
when I come to treat of the sense of hearing, are not connected 
with any other bone. 

283. I pass now to the bones of the trunk of the body. I 
shall speak first of the spinal column, or the backbone, as it is 
called in common language, as if it were all one bone. In 
some respects it does act as one bone, although it is made up 
of twenty-four distinct bones. It is the great pillar of the 
body. As such, it has the head resting on its top, and it fur¬ 
nishes support for the walls of the chest, and for the muscles 
which make up the most of the walls of the abdomen. To it 
also are fastened, as you have seen in the chapter on Digestion, 
the mass of intestines in the abdomen, and indeed to some ex¬ 
tent all the viscera both of the abdomen and the thorax. Sus¬ 
taining, therefore, as it does so much weight in so many ways, 
it stands firmly planted on its great pedestal, the strong broad 
bone of the pelvis, the sacrum. And this pedestal is supported, 
as I have before said, after the manner of a keystone, between 
the lighter spreading bones of the pelvis on either side. But 
while the spinal column acts as a strong and firmly supported 
pillar, it is necessary that it should be flexible for the different 
motions of the body. It is therefore composed of twenty-four 
bones called the vertebra , so that, as in any considerable motion 
of the column as a whole, there is but little motion between 
any two of them, the motion does not interfere with its office as 
a firm pillar. It is most free in its uppermost part, the neck ; 
it is considerable in its lower part, the small of the back; and it 
is least of all in that part to which the ribs are joined. You 
readily see the reasons for this difference in motion in different 
parts of the column. For the varied motions of the head there 
is need of a free movement between the vertebrae. Then for the 
twisting and turning motions of the body, you have the free 
movement between them at the lower part of the column, 
which is easily provided for there, because there are attached to 
that portion of it nothing but parts that are pliable. It is not 




184 


HUMAN PHYSIOLOGY. 


Vertebrae. Processes for locking strongly together. 

so with that portion of it that forms the supporting pillar of the 
framework of the chest. There is little motion here between 
the vertebrae, because the joining of the ribs to the column 
forbids it. 

But besides serving as a firm pillar, and as a flexible chain, 
the spinal column also forms a canal or tube in which the 
spinal marrow, one of the most delicate and important organs 
in the body, is securely lodged. This canal extends through its 
whole length, and from the spinal marrow included in it there 
pass out the nerves to go to all parts of the body. 

284. Having thus presented a general view of the spinal 
column, I will now give a particular description of the form 
and arrangements of the bones of which it is composed, so that 
you may understand how the various objects of this wonderful 
structure are secured. In Fig. 92 you see a representation of 


FIG. 92. 

c 



A VERTEBRA. 


one of the vertebrae ; a, being the body of the bone; b, the hole 
which forms this vertebra’s part of the canal for the spinal 
marrow ; and c, the spinous process. It is these spinous pro¬ 
cesses that make the row of projecting points seen down the 
length of the back. There are six other processes, only four of 
which you can see in the figure. Four of these processes serve 
to lock the vertebra with its two adjoining ones above and 
below, which they do so strongly, that there can be no disloca¬ 
tion of them without a fracture. Fig. 93 gives a side view of 
a vertebra. Strong ligaments bind these bones together, and 
there are very numerous muscles attached to the processes, so 








THE BONES. 


185 


Spinal column. Canal through it. Cartilages. 


that this jagged column of bones is very thoroughly enveloped 
in softer substances. 

285. In Fig. 94. you see the whole fig. 94. 

spinal column with the sacrum on which 
it stands. It is laid open by a verti¬ 
cal section dividing it into two halves, so 
as to show the manner in which the bones 
form the tube that contains the spinal 
marrow. The darkly shaded strip through 
the length of the figure represents this 
tube. It extends, you see, down beyond 
the limits of the column itself through the 
sacrum. It is bounded in front by the 
bodies of the vertebne represented as sawn 
through from front to rear, and by the 
spinous processes behind also sawn in the 
same way. In this canal.you see there 
is a row of little openings, arranged just 
behind the bodies of the vertebrae. 

Through these openings, each of which 
is between two of the vertebrae, the nerves 
go out from the spinal marrow. The ar¬ 
rangement is such, that the nerves are 
very securely guarded against the hazard 
of pressure in the movements of the verte¬ 
brae upon each other. You see also that 
there are spaces between the bodies of all 
the vertebrae. These are filled with car¬ 
tilages, which vary in thickness in differ¬ 
ent parts of the column, from one quarter 
even to three quarters of an inch, being 
thickest in the lower part of the back, 
where the backward and forward motion 
of the vertebrae upon each other is the spinal column 
greatest. Each cartilage is firmly fas¬ 
tened to the two vertebrae, between which 
they are situated, by the rough surface of the body of the bone 
which you see represented in Fig. 92. This arrangement of 
cartilages is an important provision for the motion of the spinal 
column. It contributes greatly to its flexibility. When you 
stoop forward, all of the cartilages are compressed, and when 
you rise up they return to their usual size by their elasticity. 
And besides this, they serve to diminish any shock which 

16 * 





186 


HUMAN PHYSIOLOGY. 


Spinal column shaped so as to guard against shocks. 

miglit otherwise be transmitted through the column of bones 
to the head with too great force. There is another guard 
against the injurious transmission of shocks to the brain, in the 
shape of the spinal column, the twenty-four bones being ar¬ 
ranged, not in a straight line, but in a double curve. The 
vibration, communicated upward through the spinal column, is 
thus not only lessened by the elasticity of the cartilages, but is 
also distributed in different directions by the curved arrange¬ 
ment of the bones. If the column had been made straight, 
the head would have been subject to frequent jars in the 
movements of the body, which would be disagreeable and 
often injurious. 

286. You have thus seen how three different objects, ap¬ 
parently incompatible with each other, are accomplished in the 
arrangement of the spinal column. To put twenty-four bones 
together in such a way, that they shall form a strong firm 
pillar for the whole frame, and yet they shall make a column 
or chain flexible enough for the various motions of the trunk 
of the body, and at the same time provide in this column a se¬ 
cure canal for the rod of nervous matter which moves all the 
muscles of the body, is to produce a piece of mechanism which 
far transcends any thing that has ever been contrived by the 
ingenuity of man. 

287. There remains to be noticed one especial contrivance 
in the spinal column. It is at its summit, and it is for the 
purpose of providing for the free motions of the head in various 
directions, and at the same time securing the spinal marrow at 
that part from all hazard of pressure from these motions. 
These two objects are accomplished in this way. The head in 
moving backward and forward rocks on two smooth surfaces on 
the first vertebra. But when the head moves to the right and 
left, this first vertebra moves along with the head on the second 
vertebra. And there is a tooth-like process that projects up 
from the second vertebra inside of the first, around which this 
rotary motion is performed. In Fig. 95 is represented the first 
vertebra. J. J. are the two surfaces on which the head rests, 
and rocks backward and forward. A is the opening for the 
spinal marrow. L is the strong ligament which confines the 
toodi-like process that projects upward from the second verte¬ 
bra. In Fig. 96 is the second vertebra. P is the tooth-like 
process, around which the first vertebra rotates, carrying the 
skull with it. You see it is smaller at its root than at its top. 
This smaller part is bound firmly by the ligament in the first 





THE BONES. 


187 


Arrangement of first and second vertebra*. 

vertebra. It is shaped thus to prevent its slipping out from the 
ligament. J, J, are the two surfaces on which the first verte¬ 
bra moves as it rotates around the tooth-like process. Fig. 97 
shows the two* bones together, the tooth-like process being con¬ 
fined in the ring of the upper bone. Special pains are taken to 
make this arrangement secure, that the process may not be 
in danger of pressing upon the spinal marrow at this important 
point. It is thus that the lateral rotary motion of the head and 
the forward and backward motion are secured by two joints, 
just as is done in the mounting of a telescope. The difference 
between the two cases is, that in the mounting of the telescope 
there are no difficulties to overcome, while in arranging the 


FIG. 95. 



BECOND VERTEBRA. 





188 


HUMAN PHYSIOLOGY. 


Snecial defense of spinal cord in neck of birds. 


FIG. 


mounting of the head, as we may term it, a peculiar contrivance 
and a nice adjustment are needed to prevent injury of a very 
important organ. It is'a wonderful contrivance, by which so 
much and so varied motion can be effected in the very walls that 
contain the soft and delicate spinal marrow, without injuring 
it. You will fully appreciate this, if you observe the extent and 
variety of the motions of the head and neck, executed chiefly 
with the two bones that I have described. 

288. In the neck of birds there is a contrivance of a different 
character, for* the arrangement which answers for the motions 
required by man, obviously could not secure the very free mo¬ 
tions which the bird executes with its neck. As the bird bends 
its neck at such abrupt angles in all directions, a peculiar ar¬ 
rangement of the vertebrae is necessary, to prevent the spinal 
marrow from being pressed upon. The arrangement is a sim¬ 
ple, but effectual one. I can make this plain 
to you by the rough diagram in Fig. 98. A, A, 
are two of the vertebrae of the neck laid open. 

B is the spinal canal, and C is the spinal mar¬ 
row. You observe that each vertebra is larger 
at its ends than in the middle, allowing at the 
joinings of the bones, where the motion is, a 
considerable space between the bone and the 
spinal cord. Now if each of these bones were 
of equal size throughout, and the spinal mar¬ 
row filled up the canal, you can readily see 
that when any two of these were much bent 
upon each other, there would be pressure upon 
the spinal cord ; and pressure would produce palsy, and often 
destroy life. But with the simple arrangement above described, 
free motion, almost to a right-angle in some directions, can be 
executed without pressing on the cord. And besides this, you 
can see that the cord by this arrangement will not be bent at 
an angle, as the vertebne are, but in a curve, for the spaces in 
the spinal canal at the joinings allow of a lateral movement of 
the spinal marrow at these points. 

289. It would be interesting to consider in full the variations 
in the spinal column in different classes of animals. But I will 
ouly allude to a few of them. In quadrupeds, as they have 
their heads suspended, instead of being supported, as in man, 
upon a column of bones, the spinous processes in the neck are 
very large, and project much, for the attachment of strong 
muscles which hold up the head and move it. There is also 



-A 


SPINAL COLUMN 
in Birds. 




THE BONES. 


189 


Spinal column in fishes, reptiles, and in neck of giraffe. 


FIG. 99. 



FIG. 100. 


attached to these processes, a very stout fibrous ligament, com¬ 
monly called the paxy-waxy, to assist in sustaining the head. 
In fishes the spinal column is so arranged as to 
give it a great flexibility. In Fig. 99 is repre¬ 
sented one of the vertebrae of a fish. If you 
compare it with a human vertebra, as seen in 
Fig. 92, you will see that it differs very widely 
from it. It has no transverse or side processes. 

While the human vertebra has one spinous pro¬ 
cess that projects behind, this has two /,/, one 
in front and one in the rear, or rather, according 
to the usual position of the fish, one above and 
one below. The body of the vertebra has a cup¬ 
like cavity on each side towards its neighboring 
vertebra. When, therefore, two of these vertebrae 
are joined together, their two cup-like cavities make 
one cavity of the shape of a double cone, as seen in Fig. 100. 
This is a representation of a section 
of a portion of the spine of a fish. 

The division is made so as to cut 
the vertebrae into two halves, and 
thus show these cavities. Each 
one of these contains a sac which 
is filled with a gelatinous fluid. 

This arrangement, which secures 
very great flexibility of the spinal 
column, you can examine at any 
time when you have fish on the 
table. The long spinous processes 
make the broad frame-work of the 
animal, to which its muscles are 

attached. In reptiles there is still greater flexibility of the 
spine than in fishes. This is secured in two ways, by the 
great number of the vertebrae, and by a peculiar arrangement 
of them. There are three hundred and four vertebrae in the 
boa constrictor, over three hundred in the common ringed 
snake, and over two hundred in the rattle-snake. The articu¬ 
lations of the vertebrae in reptiles are with a ball and socket 
arrangement. The forward part of each vertebra has a deep 
cup-like depression, in which plays a round smooth ball from 
the back part of the next vertebra. And as these joints are 
firmly bound together by ligaments, the spinal column is very 
strong as well as flexible. In the gracefully flexible neck of the 



SPINAL COLUMN OF A FISH. 






190 


HUMAN PHYSIOLOGY. 


Arrangement of collar-bone, shoulder-blade, and breastbone. 

giraffe we have the same ball and socket articulations of the 
vertebrae. 

290. The framework of the chest I have already described 
sufficiently in the chapter on Respiration. The breastbone, 
which is flat and of simple form in man, is much larger and 
less simple in its form in some animals. In birds it is not only 
broader, but it has a keel-shaped projection for the attachment 
of the large muscles used in flight. The clavicle , g, Fig. 86 (so 
called from its resemblance to a key,) and commonly called 
the collar-bone, is attached at one end to the top of the breast¬ 
bone, and at the other unites with a process of the scapula, or 
shoulder-blade at the top of the shoulder joint. It is a prop to 
the shoulder, pressing it outward ; and accordingly it is large in 
those animals, the movements of whose superior extremities 
tend to bring the shoulders towards each other, while it is very 
slender, or absent even, in those the tendency of whose move¬ 
ments is to keep the shoulders apart. Thus in birds the 
drawing down of the wings by the strong muscles would bring 
the shoulders towards each other, were this not prevented by 
stout clavicles. Sometimes a second bone is added for the 
same purpose. But in the horse and other similar animals, the 
pressure of the body downwards between the shoulders tends 
to separate them, and here we find the clavicle deficient because 
it is not needed. The scapula , or shoulder blade is a thin bone 
with a stout raised spine or ridge running across it, and ending 
in forming the top of the shoulder joint. It is situated differ¬ 
ently from any other bone in the body. It is imbedded in 
muscles and has a very free motion. Its design is to give free¬ 
dom of motion to the arm. It is directly connected with the 
skeleton only by its union with the clavicle. In Fig. 101 you 
see the arrangement of the clavicle, scapula, and breastbone. 
C, C, are the scapulse or shoulder-blades. A, is the upper part 
of the breastbone. B, B, are the clavicles fastened to the 
breastbone at one end, and to the shoulder-blade at the other 
end at E, which is a process of the shoulder-blade, making the 
projecting top of the shoulder-joint. D, is another process of 
the shoulder which serves for the attachment of muscles and 
ligaments. It is called the coracoid process, from its resem¬ 
blance to the beak of a crow. 

291. The upper extremity is divided into three parts, the 
arm, the forearm, and the hand. The arm has but one long 
bone, the humerus , i, Fig. 86. This has a round head which 
moves in a shallow cup formed bv the shoulder-blade. The 




THE BONES, 


191 


Collar-bones. Shoulder-blades. Bones of the forearm. 


FIG. 101. 



FIG. 102. 





















192 HUMAN PHYSIOLOGY. 

Arrangement of the bones of the forearm for rotary motion. Bones of the hand. 

shallowness of the socket is the cause of the frequent disloca¬ 
tion of the shoulder. But if there were a deep socket like that 
in which the head of the thigh-bone is, the arm could not have 
any thing like the freeness of motion that it now has. Such an 
arrangement would involve too much of a sacrifice of necessary 
uses for the sake of security. At its lower part the humerus 
makes a hinge joint with the forearm. The forearm has 
two bones, the radius, b, Fig. 102, and the ulna, a. The par¬ 
ticular arrangement of these two bones is worthy of notice. 
The hinge-like motion of the forearm upon the arm is per¬ 
formed by the ulna alone. This bone has a beak-like process, 
which works over a smooth round surface at the end of the 
humerus. It is the outside of this process which you feel at 
the point of the elbow. The other bone, the radius, has 
nothing to do with this motion. This only rolls on the ulna 
in the rotary motions of the forearm. But at the other end of 
these bones, at the wrist, the arrangement is reversed. Here, it 
is the radius on which the hand moves in a hinge-like manner, 
while the ulna at c rolls on the radius, as the radius does on the 
ulna at the elbow. You can readily see that as the radius rolls 
on the ulna at the elbow, and the ulna on the radius at the wrist, 
a very free rotary motion of the forearm is provided for. The 
combination of this motion with the motions at the wrist, the el¬ 
bow, and the shoulder, secures that almost endless variety of move¬ 
ment, which is so striking a peculiarity of the upper extremity, 
as compared with the lower. The hand is divided into three 
parts, the carpus, p, Fig. 86, composed of eight small bones, 
the metacarpus, q, composed of bones which are like the bones 
of the fingers, r. The eight bones of the carpus are firmly 
packed together, but they have a slight motion upon each 
other, and this, together with the motion of the metarcarpal 
bones, makes the hand a more easy, light, and springy instru¬ 
ment than it would be, if these bones were all consolidated into 
one. The metacarpal bones are the framework of the flat part 
of the hand, and to them are joined the first row of the bones 
of the fingers. The metacarpal bone of the thumb has a very 
free motion upon the carpus, differing in this respect altogether 
from the metacarpal bones in the body of the hand. The 
bones in the wrist and hand are bound together by very strong 
ligaments. Those which are seen in the palm of the hand are 
represented in Fig. 103. Those which you see at a, b, and c 
bind the small bones of the wrist together, and also tie them 
strongly to the bones of the forearm, the ends of which you see 






THE BONES. 


193 


Ligaments of the wrist and the hand. 


FIG. 103. 



In the Figure. The bone at b, to which so many of these liga¬ 
ments are attached, is the prominent bone which you feel at the 
beginning of the palm of the hand on the side towards the 
body. The ligament g connects this bone with the metacarpal 
bone of the little finger. At d , cZ, are ligaments which running 
across the hand bind the metacarpal bones together at their 
beginning. At e, e , are similar ligaments where the bones of 
the fingers join them. The bones of the fingers and thumb are 
strongly held together by lateral ligaments, as seen at /,/. 
The various ligaments of the wrist and hand permit a slight 
motion between the bones; and thus the hand has freedom 
and ease in its motions while it is also a very strong and firm 
instrument. 

292. The lower extremities have some resemblance to the 
upper in their structure and arrangement, but they differ from 
them in some important respects. Here firmness is the chief 
object, while freedom of motion is the great thing to be secured 
in the structure of the upper extremities. The lower extremi- 










194 


HUMAN PHYSIOLOGY. 


Bones of the leg and the foot. Arranged for firmness. 

ties are chiefly for locomotion, but the upper are fitted for a 
variety of purposes. The body is supported upon the lower 
extremities, and, therefore, the thigh¬ 
bones have sockets in the broad flar¬ 
ing bones of the pelvis m and l, Fig. 86. 

In Fig. 104 is represented a rear view of 
the thigh-bone. Its head, a, is round, 
and fits into a deep socket in the 
pelvis. At b is a depression in which 
one end of a stout short ligament is 
fastened, its other end being attached 
to the bottom of the socket. At c is 
the neck of the bone; at d and e are 
two projections to which are attached 
large muscles to move the limb. 

Along the shaft of the bone, g , there 
is a rough ridge, A, to which muscles 
are fastened; i and k are two smooth 
surfaces for articulation with the leg 
below. At t , Fig. 86 is the bone 
called the patella or kneepan, which 
answers as a defense to the joint, 
and at the same time affords a 
mechanical advantage to the muscles 
which throw the leg forward. These 
muscles are fastened to the upper 
part of the patella, and then a con¬ 
nection is formed by a strong tendon 
between its lower part and the large 
bone of the leg. You see at once 
that the leg can be thrown forward V 
with more force by this arrangement, 
than it could be if the tendon of the 
muscles passed over the front of the 
joint without any patella. I shall 
refer to this again in the Chapter on the Muscles. The leg, 
like the forearm, has two bones, v and u, Fig. 86 ; but unlike 
them they are constructed and arranged for strength, and not 
for freedom of motion. The foot, like the hand, is divided into 
three parts. The tarsus , a, Fig. 105, is that part of the foot 
which extends from the heel to the middle of the foot. It is 
composed of seven bones, the largest of which makes the body 
of the heel. The metatarsus , 6, has .five long bones reaching 











THE BONES. 


195 


Elasticity of the foot. Arrangement for oiling the joints. 


FIG. 105. 



from the tarsus to tlie toes. The toes-, c, have fourteen bones. 
The object of having so many bones in the body of the foot is 
to give a certain springiness to it, which guards against shocks, 
and facilitates motion. Its arched form also tends to secure the 
same object. In every movement of the foot there is a slight 
motion between all these bones. Thus in walking, when the foot 
first touches the ground, it does so at the heel, as represented in 
Fig. 105. Then as the body moves forward, the fore-part of the 
foot is brought down, the weight of the body at length press¬ 
ing upon the ground at the ball of the foot, b. In executing 
this movement, elasticity is given to the tread of the foot by 
the very slight motion which occurs between these many 
bones. If tlie body of the foot were all one bone it would 
manifestly be a very stiff and awkward affair, and ease and 
grace in walking would be an impossibility. With such a foot 
we should not walk much better than one does with a wooden 
leg. 

293. Before leaving the subject of the 
bones, I wall call your attention to the 
provision which is made for the easy 
movement of their joints. The ends of 
the bones are tipped with cartilage, so as 
to afford a firm but smooth surface for the 
motion of the one bone upon the other. 

Besides this provision, the ends of every 
two bones that move upon each other are 
lined with a membrane, so arranged as to 
make a blind sac. This is illustrated in 
Fig. 106, in which a and b are the ends 
of two bones, the sac, c, lying between 
them represented here as detached from 
the bone, in order that the arrangement 0 diagram 

may be clear to you. It is as if a small showing the lining of a jofet. 


FIG. 106. 






196 


HUMAN PHYSIOLOGY. 


Each fibril of a muscle supplied by a nervous tubulus. 

bladder were introduced between the two ends of the bones, 
and were fastened all over the surfaces that press together. 
The inside of this sac is kept lubricated with a bland fluid re¬ 
sembling the white of egg, so that the joint may work easily. 
This fluid is secreted by the membrane itself, and the moving 
machinery of the human system may therefore be said to oil 
its own joints. In the knee-joint, the broad surfaces of which 
are subjected to so much pressure, there are two flat pieces of 
cartilage loose in the joint, which operate like friction wheels in 
lessening the friction. There is a similar provision in the 
articulation of the lower jaw. This member does so much 
work in talking, and such heavy work in mastication, that each 
of its joints has a movable cartilage for the diminution of 
friction. Sometimes when the lubricating fluid is deficient, or 
becomes too thick, a disagreeable crackling noise is produced 
by these cartilages in the motions of the jaw. 


CHAPTER XII. 

THE MUSCLES. 

294. Having described the bones, I now proceed to speak 
of the muscles, which move them and other parts of the frame. 
I have already described the structure of muscles in § 203 in 
the chapter on Cell-Life. Each fibril, you there saw, is a chain 
of cells, and it is the shortening of all these chains of cells in a 
muscle that produces its contraction. The action of a muscle 
is dependent upon the nerves. Each fibril has a nervous fibril 
or tubulus, (§ 232.) by which its connection with the brain or 
spinal marrow is established. And each fibril is in this respect 
probably wholly separate from every other fibril. When, there¬ 
fore, the mind wills that a certain motion shall be performed, 
an impression (§ 232) is sent to each fibril of every muscle en¬ 
gaged in that motion, through the tubulus devoted to that 
fibril. When the action is a very compound one, calling into 
operation many muscles, a multitude of these impressions are 
communicated through a multitude of distinct channels or 
tubuli. The individual is not at all conscious of the compound 
nature of muscular action, and he knows nothing of the muscles 





THE MUSCLES. 


197 


Relation of muscles and tendons. Their relative size. 


which produce any particular movement, unless he has studied 
anatomy and physiology. lie wills the movement to take 
place, and at once the requisite impressions are sent along the 
appropriate channels or tubuli to their destination. These im¬ 
pressions must differ in degree or intensity in producing differ¬ 
ent amounts of motion; and they must differ in some cases in 
different parts of the same muscle, as some fibres are put in 
motion while others are not, or as some act with more force 
than others. I will not dwell here on this point, as I shall 
recur to it in another part of this chapter, when I come to 
speak of the compound character, and the varieties of motion. 

295. Muscles commonly end in tendons, which, as they are 
white and shining, are quite in contrast with the red muscular 
fibres. The tendons have in themselves no power of contrac¬ 
tion, but are mere passive cords. They have the same relation 
to the muscles, that ropes have to the men that pull them. 
They are of various shapes, according to circumstances. Long 
and slender tendons may be seen on the back of the hand in 
thin persons, the muscles that pull them being in the full arm 
above. The tendons are not bounded by a distinct line where 
they join the muscles, but tendinous and muscular fibres inter¬ 
twine, so that they appear to run insensibly into each other. 
Tendinous fibres also mingle in the same way with the fibres of 
bone, making so strong an union, that a great force exerted in 
pulling on the tendon will sooner effect a rupture of the tendon 
or the bone, than a separation of the connection between them. 
The tendons are very strong, being made of very condensed 
fibrous substance. The tendon of a muscle is, therefore, much 
smaller than the muscle itself. This is a circumstance of much 
importance in the arrangement of the moving apparatus of our 
frames. The bulky muscles and the slender tendons, are so 
arranged, for example, in the limbs, as to give them both free¬ 
dom of motion and beauty of form. The muscles that move 
the fingers help to make up the full part of the arm, while 
their slender tendons occupy but little space as they play over 
the bones of the wrist. If there were no tendons, and the 
muscles were extended to the parts which they move, the hand 
would be a large cumbrous mass, instead of the light and agile 
thing that it is now. For the muscles would of necessity be 
continued of their full size, and, therefore, the bones would of 
course be very large in order to afford an attachment to the 
muscles. 

296. In the action of the muscles upon the bones, we have 

17 * 





198 


HUMAN PHYSIOLOGY. 


The three kinds of lever exemplified in the action of muscles. 

examples of the three kinds of levers treated of in natural phi¬ 
losophy. Some of these I will now notice. The first kind of 
lever has the fulcrum between the weight and the power, as 
•^presented in Fig. 107. F is the fulcrum, W the weight, and 


FIG. 107. 



P the power. You have examples of this lever in the common 
pump handle, the beam of a pair of scales, the crowbar, as 
commonly used, scissors, &c. You have an example of this form 
of lever in the human body, in the action of the muscles in 
moving the head back and forth on the top of the spinal 
column. In this case, when the head is moved forward, the 
top of the spine is the fulcrum, the weight to be moved is the 
back of the head, and the power is the contraction of the muscles 
that bow the head forward. When the head is bent backward, 
the power is the contraction of the muscles behind, and the 
weight is the front part of the head. The muscles that move 
the head backward are stronger than those that move it for¬ 
ward. It is necessary that it should be so, for there is more of 
the head in front of the point of support or fulcrum than there 
is behind it. Hence, when sleep relaxes the muscles, if we are 
sitting up the head foils forward. 

297. In the second kind of lever the weight is between the 
fulcrum and the power, as represented in Fig. 108. The com¬ 
mon wheelbarrow is an example of this form of lever. You 
have an example of it in the body in the raising of the heel 

FIG. 108. 



SECOND KIND OF LEVER. 







THE MUSCLES. 


199 


Motion of the foot in walking. 


from the ground in walking. In doing this the weight to be 
raised is the whole body, the foot being the lever, and the 
forward part of the foot being the fulcrum. This will be made 
elear by Fig. 109. W is the large bone of the leg sustaining 


FIG. 109. 



4 ? 


the weight of the body; F, is the fulcrum, the forward part of the 
foot that presses on the ground as the heel is raised; and P, is 
the large muscle in the calf of the leg, the power that raises 
the heel, the end of the lever. 

298. In the third form of lever the power is between the 
weight and the fulcrum. A common example of this is seen 
in the raising of a ladder. The fixed foot of the ladder is the 
fulcrum, the ladder itself is the weight, and the power is ap¬ 
plied as far from the fulcrum as it can be. Fig. 110, represents 

FIG. 110. 



THIRD KIND OF LEVER. 


W 


a lever of this kind. This form of lever is more frequently 
used than the other forms in the human body. We have an 
example of it in bending the forearm upon the arm as seen in 
Fig. Ill, in which 1 is the bone of the arm; 2, the tones of 
the forearm ; 4, the muscle which bends the forearm upon the 
arm; 5, its double headed attachment above; and 6, its at- 












200 


HUMAN PHYSIOLOGY. 


Twv objects aimed at in muscular action ; quickness and power. 



FIG. HI. 


tachm j nt to the radius, one of the bones of the forearm. In this 
case the fulcrum is at 8, the joint of the elbow, the weight is 
the hand with whatever it holds, and the power is applied at 
the point where the tendon is fastened to the ulna, that is, as in 
the case of the ladder, between the fulcrum and the weight. 
The muscle which straightens the forearm upon the arm is 
represented at 1 . I shall remark upon this in another con¬ 
nection. 

299. In the management of the three kinds of levers there 
are two different objects aimed at under different circumstances. 
One object is to move a great weight with a small power. 
Here quickness is not aimed at, but the weight is moved slowly. 
The other object is to move the weight quickly, an object in¬ 
consistent with the moving of any very heavy weight. When 
the object is to move a heavy weight slowly, the lever is so 
managed as to get a good purchase, as it is expressed. Thus 
in the case of the lever of the second kind, Fig. 108, if the 
weight be a heavy one, the power is commonly applied at some 
distance from the weight. The nearer the power is to the 
weight, the greater must it be to move the weight. The smaller 
the power, the further must it be from the weight in order to 
raise it. But though a small power if at a distance from 
the weight answers to raise it, yet in this case the power must 
move through a considerable space to move the weight but 
little; while to raise the weight to the same height, a power 
nearer to it passes through but little space. This will be made 
clear to you by Fig. 112. F is the fulcrum, and W the weight. 
If the lever, A, be raised to the line, B, the dotted lines will 
show the different spaces which the power passes through, ac¬ 
cording to its distance from the weight. If the power be at P, 









THE MUSCLES. 


201 


Quickness more often important than power. 


FIG. 112. 



it passes through the space indicated by the dotted line a in 
moving the weight W to c. But if it be at it passes through 
a much shorter space, b , in raising the weight to the same 
height. The more important, therefore; in this form of lever 
quickness of movement is, the nearer to the weight is the 
power applied. Let us look at the application of these prin¬ 
ciples to the example of this kind of lever, which I cited from 
the human body, represented in Fig. 109, the raising of the 
weight of the body on the foot in walking. The power is here 
applied quite near to the weight, for quickness in raising the 
heel in walking and running is of great importance. By hav¬ 
ing the heel project farther behind, the muscle could be at¬ 
tached farther from the weight, and thus act with more power. 
But there would in this case be a sacrifice of quickness of move¬ 
ment, and besides this, the lengthened heel would present a 
very awkward and ugly appearance. 

300. But it is in examples of levers of the third kind that 
we find these principles best illustrated. This form of lever is 
much more often used in the mechanism of the muscles than 
the other forms. I refer you to the example given of this lever 
in the action of the biceps muscle in bending the forearm, as 
shown in Fig. 111. In this case it is of much more importance 
to move small weights quickly, than to move heavy ones slowly. 
Therefore the power is applied quite near to the fulcrum. The 
tendon of the biceps, as you see, is fastened to the main bone 
of the forearm near the fulcrum, the elbow. You can readily 
see that the point where the power is applied would pass 
through but a little space, in moving a weight through a con¬ 
siderable one. The lower jaw, in its upward motion, is a lever 
of the same kind. In this case, force rather than quickness is 
required in breaking and grinding the food. Here, therefore, 
the power, the action of the muscle, is applied farther from 
the fulcrum than in the case of the biceps muscle of the arm, 







202 


HUMAN PHYSIOLOGY. 


Force most important in the case of the lower jaw. 

and nearer to the weight to be moved, or the point where the 
resistance is which is to be overcome. It is applied also in a 
different direction, a point which I shall however speak of in 
another connection. The muscles which move the lower jaw 
upward can be seen in Fig. 113. One is the large spreading 


FIG. 113. 



MUSCLES OF FACE AND NECK. 


muscle b, the swelling of which, in its contraction, we can feel, 
if we place the fingers on the temple while moving the lower 
jaw upward. The other is the short strong muscle c, the front 
edge of which is so far forward, that one-third at least of the 
lower jaw-bone is embraced by this muscle. Now, if you com¬ 
pare this bone as a lever with the forearm as acted upon by 
the biceps, you will at once see that the power is applied much 
nearer to the weight, or the resistance to be overcome, in the 
case of the jaw, than in the case of the arm. It is so even when 
the resistance to be overcome is at the front teeth ; and it is 
much more so when the resistance is at the back part of the 
mouth, as when we are grinding our food. Here, indeed, a por¬ 
tion of the muscular force is brought to bear upon the resistance 
in a direct line. It is not merely because the back teeth aro 











THE MUSCLES. 


203 


Mechanical disadvantage in muscular action. 

stronger than the front ones, but also because the power is nearer 
the resistance, that we can crack a nut more easily with the 
back, than we can with the front teeth. 

301. It is clear that the biceps muscle acts, as it is expressed, 
at a mechanical disadvantage, if we regard mere power or force, 
and leave out of view quickness of motion. If it were inserted 
further down on the forearm, nearer the hand, it could raise 
much greater weights than it now can. And the same can be 
said of most of the other muscles of the body. But force is 
sacrificed for the sake of quickness in most cases, because the 
latter is more important. In the few cases in which force is 
more important, as in the case of the lower jaw just cited, the 
reverse arrangement is provided. The gain in quickness in the 
arrangement of the biceps muscle can be illustrated on Fig. 114. 

FIG. 114. 

c 



F being the fulcrum, the power in raising the weight, W, to c, 
if acting at P, passes through the space indicated by the dotted 
line a. But if it act at y>, it will pass through all the space 6, 
and of course raise the weight mom slowly than when acting at P. 

302. Most of the muscles work at a mechanical disadvantage 
in another way. I refer to the direction in which the muscle 
acts on the bone to be moved. This is seldom at right angles, 
and therefore a considerable part of the force exerted is lost. 
This can be made clear to you by Fig. 115. Let b represent 
the bone of the arm, and r its fulcrum, or point of support in 
the shoulder. You readily see that if the bone be acted on by 
a muscle, m, at right-angles to it, it will require less force to 
move it to a given point than would be required if the same 
muscle were placed in the position represented by n. For the 








204 


HUMAN PHYSIOLOGY. 


When loss in power, gain in quickness. 


FIG. 115. 



muscle n, acting obliquely on the bone would expend a part of 
its force in pressing the end of the bone upward against the 
socket of the joint at r. 

303. But in this case also, what is lost in power is gained in 
quickness of movement. This can be shown on the figure. 
We will suppose that the muscle contracts or shortens itself the 
half of the length of the tendon. If the muscle were placed as 
at m, the bone would be carried to the line a, c. But if the 
muscle be placed as at n, the same degree of contraction would 
raise the bone to the line a, d, the point of the bone where the 
tendon of the muscle is attached moving in the curved line as 
marked. The resistance to be overcome, of course, requires 
much more power for the obliquely placed muscle, n , to raise 
the bone to the line a, d , than for the muscle m to raise it to 
a, c ; and therefore a much larger muscle is needed than there 
would be if it acted at right-angles to the bone as at m. And 
the muscle which raises the arm at the shoulder, acting: as it 
does at so great disadvantage, is a very large muscle. The 
muscle, n, in the figure represents only the line of its action, 
and not at all its shape. If you observe the various motions of 
the arm in which this muscle has a part, you will appreciate 
the necessity of so arranging it as to secure quickness of move¬ 
ment. This was the chief object to be aimed at in its arrange¬ 
ment; and the second and less important object, power, is 
secured, so far as it is needed, by simply making the muscle a 
large one. 

304. The mechanical disadvantage, which I have noticed as 
resulting from the oblique action of the muscles, is in part ob¬ 
viated by a very simple contrivance. It is done by making the 


4 





THE MUSCLES. 


205 


Contrivance to change the direction of force. 



FIG. 117. 

m.J 


i... 


tendon of the muscle work over an enlargement of the bones at 
the joints. The operation of this contrivance can 
be made clear by Figs. 116 and 117. Let r and FIG - 116 * 
o (Fig. 116) be the two bones of a joint, and let 
the muscle m be attached to the bone o at i. As 
it contracts, almost all its force will be spent in 
drawing the bone o upward against the bone r, 
because it acts almost entirely in a line with the 
bones. But let the ends of the bones be en¬ 
larged as in Fig. 117, and you can see that the 
direction of the tendon of the muscle m is so 
changed where it is attached to the bone, that the 
muscle can now very easily make the lower bone 
turn upon the upper. The enlargement then of 
the bones at the joints, which is needed to give 
the requisite extent of surface for working them, 
answers also another good purpose in thus alter¬ 
ing the direction of force in the muscles. In the 
case of the knee-joint there is an additional contrivance for 
making this change of direction still greater. A movable bone, 
the patella or kneepan, besides acting as a protection to the 
joint, effects also the purpose referred to. The manner in which 
it does this can be made plain by Fig. 118, in which a represents 
the end of the thigh-bone; 6, the end 
of the large bone of the leg articulat¬ 
ing with it; c, the patella ; d , the large 
tendon which comes from the muscle 
above, and is fixed into the patella; 
and e , the tendon which goes from 
the patella to the large bone of the 
leg below. The dotted line shows 
how much the direction of the force 
of the muscle is changed by this ar¬ 
rangement. The movement performed 
by this muscle is throwing the leg and 
foot forward, which it is by the above 
arrangement of the patella enabled to 
do with great ease in walking, and 
with great force in the act of kicking. 

305. The pulley is used in the ar¬ 
rangement of the muscles, though by 
no means as often as the lever. It 

serves, whenever it is used, to give the force a different direction 

18 


FIG. 118. 











206 


HUMAN PHYSIOLOGY. 


The pulley-arrangement in muscles. 

from what it would otherwise have. I will cite but a few 
examples. At the wrist and the ankle there are broad liga¬ 
ments, which bind down the tendons of the muscles, and sus¬ 
tain to them the relation of pullies. If it were not for these 
ligaments the tendons at these joints would fly out continually 
when the muscles are in action, making projecting cords under 
the skin. And if the skin were removed, the tendons would 
be in a position similar to that represented at A, in Fig. 119. 


FIG. 119. 



In this Figure, C is the tendon of the great toe in its position as 
bound down by ligaments. Now if the muscle were in the 
position represented by A, it is plain that it would act at a 
greater mechanical advantage than in the position G; but the 
toe would not be moved as quickly; and besides, if the tendons 
projected in this way, the foot would be a very cumbrous piece 
of machinery, compared with what it is now, with the tendons 
bound down around the slender ankle. So that both beauty 
and use are secured by the arrangement. 

306. There is a beautiful application of the pulley in the 
case of the muscle that draws down the lower jaw, called 
the digastric muscle. It is represented in Fig. 120, in which 
a is one end of the muscle attached behind the ear, and b is the 
other end attached to the inside of the lower part of the chin. 







THE MUSCLES. 


207 


Manner in which the lower jaw is drawn down. 


FIG. 120. 



DIGASTRIC MUSCLE. 


It is muscular at the two ends, and tendinous in its middle 
part. This middle part runs through a loop or ring in a small 
muscle as represented in the Figure. This little muscle is 
fastened above to a small process of bone under the ear, and 
below to the hyoid, or U-shaped bone, c, which is situated just 
above the larynx. Now when the jaw is to be drawn down, 
the two fleshy ends of th epigastric muscle contract, and the 
middle tendinous part works in the ring provided in the little 
muscle. This muscle is so slender, that its loop is of itself alone 
hardly strong enough, as we should suppose, for the tendon of 
so large a muscle as the digastric to work in. And we accord¬ 
ingly find that there is an additional security in a strong liga¬ 
ment, which fastens the tendon of the digastric muscle to the 
hyoid bone. This ligament (which I have not represented in 
the figure, because it would confuse your view of the pulley- 
action of the parts) is sufficiently long to allow of all the 
freedom of motion necessary to drawing the jaw downward. 
You see at once that one object of this arrangement of the di¬ 
gastric muscle is to secure beauty of form in the neck. A 
muscle extending from the top of the chest to the chin in a 
straight direction would very effectually draw down the lower jaw, 
but it would be a great deformity. This is avoided by the pulley- 
arrangement of the digastric muscle. But this muscle answers 
another purpose besides drawing down the jaw. If while the jaw 
be held fast by muscles which draw it upward, the digastric 
contracts, it will draw up, as you can readily see by the Figure, 
the hyoid bone, c, and with it, of course, the larynx which is at- 




208 


HUMAN PHYSIOLOGY. 


Straight and oblique muscles of the eye. 

tacned to it. Now precisely this set of motions occurs when wa 
swallow. The mouth is shut by the drawing up of the jaw, 
and then the contraction of the digastric muscle draws up the 
larynx, as you can perceive if you place your fingers on the 
larynx, or Adam’s apple, as it is called, when you perform the 
act of swallowing. The little muscle in which the loop is, 
renders some assistance to the digastric in thus drawing up the 
hyoid bone and the larynx, as you can see by the Figure. 

307. I will notice one more example of the pulley-ar¬ 
rangement. It is in the eye. There are six muscles that 
move the eye-ball. Five of them are represented in Fig. 121. 
There are four straight muscles, three of which are marked 


FIG. 121. 



<z, b , c; the fourth is behind b , the upper edge of it only 
being seen in the Figure. These muscles are at their origin in 
the back part of the socket of the eye arranged round the optic 
nerve, and passing forward are attached to the sclerotic coat, 
the firm white coat of the eye. The two lateral muscles, 6, and 
its opposite, move the eye to the one side and the other, and 
the two muscles, a. and c, perform the up and down motions. 
But there are certain oblique rolling motions of the eyeball 
which can not be executed by these straight muscles. For these 
motions two muscles are provided, one of which has a pulley- 
arrangement, as represented in the Figure. This muscle, s, has 
a long tendon which passes through a ring in cartilage in the 
roof of the socket, and then turning back is fastened as you see 
to the upper part of the eyeball. This muscle, as stated in the 
chapter on the Nervous System, is under the direction of one 
nerve alone. It is an involuntary muscle which performs the 
insensible rolling motions of the eyeball, and like the other in¬ 
voluntary muscles of the body, is at work while we are asleep, 
as well as when we are awake. It is the muscle which rolls 
about the eye tremulously when it is open in the insensible 
state sometimes produced by disease. 





THE MUSCLES. 


209 


Opposing muscles. Compound muscular action. 

308. Every muscle performing a motion has its opposing 
muscle or muscles, which perform the opposite motion. In the 
case of any two opposing muscles the one must be in some 
measure relaxed while the other is in action. Thus in alter¬ 
nately bending the elbow, and straightening it, there is alternate 
action and relaxation in the two opposite muscles 4 and 7, as 
represented in Fig. 111. So in moving the head back and 
forth the muscles in front and rear are alternately contracted 
and relaxed. Paley very aptly compares this to the action of 
two sawyers in a pit, as they move the saw back and forth. 
The comparison, however, is not strictly true, because the re¬ 
laxing muscle is never wholly relaxed. There is indeed in every 
muscle some amount of contraction which is independent of 
action through the nerves, whether it be reflex, or produced by 
the will. For this reason the muscles cut off in amputation 
of a limb retract. So also if the muscles on one side of the 
face be palsied, the muscles on the other side draw the mouth 
to that side. The mouth is held in the middle of the face by 
the equal action of pairs of muscles. The head, too, is held in 
equilibrium in the same way. In what is called wry-neck, this 
tonic contraction, as it is sometimes termed, is greater in the 
muscles on one side than it is on the other. In some cases a 
cure can be effected only by dividing the contracted muscles. 
In strabismus, or squinting, one of the straight muscles of the 
eyeball contracts too strongly for its opposing muscle, and as 
in wry-neck, dividing the contracting muscle is often necessary 
to remedy the difficulty. 

309. Most motions are not performed by single muscles, but 
by the joint and agreeing action of several, and sometimes 
many muscles. And as these muscles may vary to a great 
extent in their degree of contraction, the motions produced by 
them are not only compound, but are exceedingly varied. To 
illustrate this compound and varied character of motion, I will 
refer to a single example in which only two muscles are con¬ 
cerned in the motion. In Fig. 113 you see a pair of muscles, 
one of which is marked A, which extend from the large protu¬ 
berances behind the ears to the top of the breast-bone. In the 
neck of a thin muscular person these muscles are very promi¬ 
nent. When they contract equally , the head is bent straight 
forward in the middle line between the muscles, and a line 
drawn from the middle of the forehead down to the breast¬ 
bone would strike exactly at the point where these two muscles 
unite. But if one muscle contracts more strongly than the 

18* 




210 


HUMAN PHYSIOLOGY. 


Variety in muscular action. Exemplified in the tongue. 

other, the head as it bows forward bows towards the side on 
which is the strongest contraction. And as the degrees of 
contraction in these two muscles may be endlessly varied, so 
there may be an endless variation in the degree of inclination 
of the head to one side or the other, as it is bent forward. If 
then so great a variety in the direction of motion may be pro¬ 
duced by variation in the degrees of action in two muscles, you can 
readily see that an almost infinite variety of motion must result 
from this variation, where many muscles are called into action. 

310. I know not any part of the body, which exemplifies in 
so palpable a manner the compound and diversified character 
of muscular motion as the tongue. It is mostly a bundle of 
muscular fibres, apparently mingled together in confusion, but 
really arranged in perfect order, so that it can be moved with 
great definiteness in all directions, forward, backward, upward, 
downward, to either side, and in all intermediate directions. If 
you stand before a glass, and opening your mouth, move the 
tongue rapidly about in all these directions, you think of a har¬ 
lequin performing his antics. But all this wonderful variety of 
movement is produced in obedience to the definite action of 
nerves, whose fibres are mingled with the muscular fibres of the 
tongue. And in order to produce each motion there is an agree¬ 
ment of action not between merely many of these fibres, but 
between multitudes of them. 

311. With the view which I have given you of the compound 
and varied character of muscular motion, you are prepared to 
take a general survey of the muscular system. For this pur¬ 
pose I call your attention to a side view of the muscles of the 
body as presented in Fig. 122. I must premise, that you can 
get no idea from this Figure of the number of the muscles in 
the body, for you see here only the outer layer of muscles, and 
there are many muscles concealed by them. You observe that 
they are of various shapes and sizes, according to the motions 
which they are designed to produce, and the circumstances 
in which they are placed. They are round, long, short, flat, 
fan-shaped, circular, serrated, &c. I will point out some 
of them. At a is the very large muscle that makes the 
fleshy prominence at the upper part of the arm, and the 
office of which is to raise the arm, carrying it out from the 
body. You observe that its fibres are not all arranged alike 
but lie in different directions. The result is, that while the 
arm is raised by the muscle as a whole, it may be carried at 
the same time forward or backward by the varying action of 





THE MUSCLES, 


211 


External layer of the muscles of the body. 


FIG. 122. 



MUSCLES OF THE BODY. 











212 


HUMAN PHYSIOLOGY. 


General description of the muscles in various parts. 

these different fibres. There are many of the muscles of the 
body which are made thus to produce various results by 
variation of the action of different parts of the same muscle. 
And the regulation of this variation by the nerves is one of 
the most wonderful and mysterious things which we find in 
our study of the nervous system. For each fibre in the cases 
referred to is told, as we may express it, just how much it must 
do in order to produce the requisite general motion of the 
muscle. It is manifestly much more wonderful thus to pro¬ 
duce various but accurately graduated contraction in different 
parts of the muscle, than to produce an uniform contraction in 
all its fibres. 

312. I go on with my notice of the particular muscles. At 
b is the biceps muscle, which bends the forearm upon the arm, 
and at e is another muscle that assists the biceps. At e is the 
large muscle in the back of the arm, which acts in opposition 
to the biceps, and straightens the forearm upon the arm. At 
d is a muscle which rolls the radius outwards, and thus turns 
the palm of the hand upward as seen in the Figure. At g is a 
very large broad muscle coming from the whole length of the 
back, and at the axilla or arm-pit, its fibres are collected, 
twisted, and folded upon each other. The muscle is fastened 
by a stout tendon to the upper and back part of the bone of 
the arm, and its office is to pull the arm backwards and down¬ 
wards. At h is a serrated muscle, which rising from the ribs, 
goes to the shoulder-blade, and serves to draw the shoulder- 
blade forwards. Ate is one of the broad muscles of the ab¬ 
domen. At l and k are two large muscles that move the 
thigh. At o and y>, as seen on the right thigh, and at n , as 
seen on the left, are three large muscles, which are fastened to 
the kneepan, and serve to throw the leg forward as described 
in § 304. At q is the tendon that forms the outer hamstring, 
and at r are the two tendons which form the inner one. The 
muscles to which these tendons belong, serve to bend the leg 
upon the thigh, drawing it upward and backward. At 6* is 
the muscle which makes the bulk of the calf of the leg. It 
lifts the heel upward and backward, and it is seen in action in 
the right leg of the Figure. Its strong tendon which is at¬ 
tached to the top of the heel bone is called, on account of its 
strength, the tendon of Achilles. This muscle is in Fig. ] 09. 
the power P which raises the weight of the body, W, on the 
fulcrum, F, as the heel is raised from the ground in walking. 

313. In Fig. 123 you have a rear view of tbe muscles. At 




TIIE MUSCLES. 


21 


Rear view of the external layer of the muscles. 


* 


FIG. 123. 



REAR VIEW OF THE MUSCLES, 











214 


HUMAN PHYSIOLOGY. 


Some muscles are very small. Symmetrical arrangement of the muscles. 

a is a very broad muscle, wliicli rising from the back is attached 
to different parts of the shoulder-blade. You can see that 
this irregularly shaped muscle, will move the shoulder-blade 
variously, according to the various action of the different fibres 
of the muscle, which run in so different directions. At c you 
see the rear part of the muscle that raises the arm. At b is 
the extensive muscle that you saw in Fig. 122 at g, which 
draws the arm backward. At e is a large muscle that draws 
the thigh backward. At g, h, and / are the muscles whose 
tendons form the two hamstrings. At i is the muscle that 
forms the calf of the leg, and raises the heel. 

314. 1 have thus described to you a few of the principal 
muscles in the body, that you may have some idea of the modes 
in which they act, and the manner in which they are arranged. 
Those which I have described are all muscles of considerable 
size. But there are some exceedingly small muscles in the 
body, producing some very delicate motions. • For example, all 
the variations in the note of the voice result, as you will see in 
the Chapter on the Voice, from the variation of tension of 
the vocal ligaments, which is regulated by certain very small 
muscles. As the laborer sings over his work, great is the con¬ 
trast between the delicate action of these little muscles, and the 
strong action of the muscles of his stalwart arm. A variation 
of less than a hair’s breadth in the contraction of the muscles 
of the vocal ligaments suffices to produce an appreciable differ¬ 
ence in the note of the voice. 

I have thus far spoken of the bones especially as being 
moved by the muscles. But other parts are moved by them 
also. In the case of the voice, just alluded to, the little muscles 
move cartilages to which the vocal ligaments are attached. 
The tongue and the palate are moved by muscles. Muscles 
move the skin. In man this is generally very much confined 
to the face. The mouth, the eyelids, the eyebrows, <fcc., are 
moved by muscles. In many animals the skin is moved ex¬ 
tensively by muscles, as for example when the horse shakes his 
skin to get rid of the biting flies. 

315. In the arrangement of the muscles great regard has 
been paid by the maker of our bodies to convenience and sym¬ 
metry, and not merely to mechanical advantages. Thus, the 
muscles moving the fingers are mostly placed in the forearm, 
while the slender tendons pass over the surface of the bones in 
the wrist. The flowing outline of the arm is thus secured, and 
the hand is made a light, and at the same time, a strong ap- 




THE MUSCLES. 


215 


Contrivances in muscles and tendons of the hand and foot. 


paratus. The same can be said substantially of the arrange¬ 
ment of the muscles and tendons in the leg and foot. There 
is one arrangement in the foot which is worthy of especial no¬ 
tice. There is a muscle in the fleshy part of the leg, which by 
a long tendon, divided in the foot into four tendons, bends the 
last joints of the toes. There is also a short thick muscle in 
the bottom of the foot which joins the tendons of the first 
named muscle, and assists it in bending the toes. It is as if 
two different sets of men were placed in two different positions, 
with ropes arranged so as to pull in the same direction. The 
question arises, why the toes are not bent by a single muscle, 
lodged conveniently in the fleshy part of the leg. The reason 
probably is, that the muscle placed in the sole of the foot is 
needed there as a filling up in the arch of the foot, and so the 
force necessary to bend the toes is divided between the two 
positions. 

316. There is another contrivance in this muscle that bends the 
toes which I will notice here. Its four tendons pass to the last 
bones in the toes, and in doing so they go through the tendons 
of the muscle that bends the second joints. These latter divide 
at their ends where they join the bones for this purpose. A 
similar arrangement also is made in the fingers for the tendons 
of the second and third joints. This is represented in Fig. 124, 


FIG. 124. 



in which e is the tendon which goes to the last bone c through 
the division in/, which goes to the second bone b. It is mani¬ 
fest that this is the best way of packing the tendons, as we may 
express it. Any other conceivable arrangement would add to 
the bulk of the finger. As they are represented in the figure 
they are raised up, instead of being closely packed down upon 
the bone, as they are in reality. 

317. I have already alluded to the fact that many muscles 
unite in producing most of the movements of the body, and 
that, as they vary in the degrees of their contraction, the 
variety of motion resulting from both these causes, is exceed- 








216 


HUMAN PHYSIOLOGY. 


Complicated action of associated muscles. 

ingly great. I will now call your attention more particularly 
to these points, as you can more readily appreciate them after 
the general view which you have taken of the muscular system. 
Even when only a part of the body is put in motion, there are 
often many muscles engaged in the act. Take, for example, 
the act of swallowing, which I have described in §78 in the 
Chapter on Digestion. In this compound act the muscles of the 
jaw close the mouth, the tongue thrusts the food back into 
the throat, the digastric muscle (§ 306), pulls up the larynx, 
and the epiglottis is at the same time shut down by muscles 
upon the opening into the larynx, to let the food slide over it. 
In speaking and singing the action of the muscles is much more 
complicated than in the act of swallowing. The muscles of the 
chest work the bellows of the organ (for such is the relation of 
the chest to the musical instrument, the larynx,) the muscles of 
the vocal ligaments put them in the state of tension required 
to produce the note intended, the muscles of the epiglottis raise 
it to let the sound out, and the muscles of the throat, palate, 
tongue, and lips, give articulation to the sound as it comes from 
the larynx. And observe, that some of the same parts are en¬ 
gaged in the act of speaking that are engaged in that of swal¬ 
lowing, but are put in different positions for the two acts. 
Thus, the epiglottis is raised up when we speak, and is shut 
down when we swallow, and the larynx is raised up when we 
swallow, and is drawn down again when we speak. And how 
quickly we pass from the one act to the other, as we mingle 
our talking and eating together! And we do it with such 
facility and precision, that it is a very rare accident that a crumb 
or a drop slips into the larynx. Observe farther, that when we 
take a breath, as well as when we speak, the epiglottis must be 
raised, the air passing in, instead of passing out as in speaking. 
The parts, therefore, are often engaged in these different acts, 
not only distinct from each other, but inconsistent with each 
other also, and they change from one of these acts to another 
so readily, that as we eat, and breathe, and talk, we are con¬ 
scious of no disturbance, and scarcely ever of any effort in the 
change. No change of action in any machinery of man’s in¬ 
vention can be at all compared with this in the precision and 
facility of the change, much less in its complicated character. 

318. But if there be complication and variety of action when 
but one part of the body is put in motion by the muscles, there 
will be vastly more when the muscles of the body as a whole 
are brought into action. If you look at Fig. 122, you see the 




THE MUSCLES. 


217 


Constant change in complicated muscular movements. 

muscles generally in more or less action, and the action of each 
one has its particular relation to the attitude assumed. If now 
the attitude be varied, this particular relation of each muscle 
must be varied also. If, for example, the right foot be carried 
forward so as to bring the weight of the body on to that foot, 
instead of the left, on which it now rests, as represented in the 
Figure, all the muscles of the frame will have a different rela¬ 
tion in their action. And not only this, but while the body is 
changing from the one attitude to the other, there will be a 
continual change of this relation. At no one moment during 
the act or motion, which changes the attitude, will the state of 
contraction in each muscle be precisely the same, that it is at 
any other moment. Thus, the state of the muscles in the be¬ 
ginning of the change of attitude is altogether different from 
what it is when the movement is half accomplished. And the 
same can be said of any other two points in the progress of the 
movement. The same is true of any other general action 
of the muscles. Thus, if one is pulling with his feet braced, the 
muscles do not remain in the same relative condition all the 
time, but as the body which is pulled yields, the relative tension 
of the muscles is changed every moment. But there is no 
movement which exemplifies this change of relative condition 
of the muscles so well as that of balancing. If with the views 
which I have presented in your mind, you observe some one 
who is skillful in balancing, you will be impressed with the ever 
changing but precisely regulated degree of tension in the differ¬ 
ent muscles, and with the variety of combination in their 
action. 

319. I will not comment to any extent upon the general 
movements and attitudes of the body. But I 
will here simply call your attention to one 
mode of action, in which a large number of 
the muscles are called into play, on account of 
its analogy to an expedient often used in me¬ 
chanics. I refer to what is called the toggle- 
joint. This I will explain. Let c, a , and c, b , 
represent two bars connected together, like a 
carpenter’s folding rule, by a hinge or joint at 
c. Suppose the two ends, a and 6, to be fitted 
into the two blocks represented in the Figure. 

If now the block at b is fixed, and the block at 
a is movable, and force be applied to the joint 
c carrying it towards d , the block at a will be toggle-joint, 

19 


FIG. 125. 

a 



b 











218 


HUMAN PHYSIOLOGY. 


Examples of the toggle-joint in muscular movements. 

pressed upward with considerable power. If on the other 
hand, the block at b is movable, and that at a is fixed, the block 
at b will be pressed downward. We see this latter form of the 
contrivance applied in printing presses. In the human body 
this toggle-joint is used in both ways. When one stoops to 
take a heavy weight upon his back or shoulder, he puts both 
the knee and the hip-joints into the condition that the toggle- 
joint is when it is bent; and then as he straightens up, the 
weight is raised by an action of the joints precisely similar to 
that of the toggle-joint in machinery. In the case of the knee, 
the straightening of the joint is done by the muscles on the 
front part of the thigh, that draw up the kneepan with the 
tendon attached to it. This is using the principle of the toggle- 
joint in pressing wpward. It is also sometimes used in pressing 
downward. In crushing any thing with the heel, we give great 
force to the blow on the principle of the toggle-joint, by flexing 
the knee and straightening the limb as we bring down the heel 
upon the thing to be crushed. In pushing any thing before us, 
we bend the elbow as preparatory to the act, and then thrust 
the arm out straight, thus exemplifying the toggle-joint. The 
horse gives great force to his kick in the same way. The great 
power exerted by beasts of draught and burden is to be referred 
very much to the principle of the toggle-joint. When a horse 
is to draw a heavy load, he bends all his limbs, especially the 
hinder ones, and then as he straightens them, he starts the 
load. In this case the ground is the fixed block of the me¬ 
chanism, the body of the horse to which the load is attached is 
the movable one, and his limbs are so many toggle-joints. By 
this application of the principle we see draught horses move 
very heavy loads. “ So, (admitting fable to be fact,”) says Dr. 
Griscom, “ when the farmer, in answer to his petition for assist¬ 
ance, was commanded by Hercules to exert himself to raise his 
wagon from the pit, he placed his shoulder against the wheel, 
and drawing his body up into a crouching attitude, whereby all 
his joints were flexed, and making his feet the fixed points, by 
a powerful muscular effort, he straightened the toggle-joints of 
his limbs, and the wheel was raised from its bed of miry clay. 
His horses at the same moment extending their joints, the 
heavily laden wagon was carried beyond the reach of farther 
detention.” 

320. The hand is the most wonderful of all parts of the 
body, in regard to variety and complication of movement 
There are over fifty muscles, which are engaged in the variou 





THE MUSCLES. 


219 


Great variety of action in the muscles of the hand. 


motions of the upper extremity, all of which, of course, have 
more or less reference to the hand. Indeed the hand is the 
part of the upper extremity to which all its other parts are 
tributary, and therefore we may properly consider all these 
muscles as in a great measure belonging to the hand. If now 
you call to mind the fact, that each one of these muscles can 
vary the amount of its contraction in all degrees, from the most 
powerful action down to the slightest movement, you can 
readily see that fifty muscles with this power of variation can 
produce an almost endless number of combinations of motion. 
The variety would be exceedingly great, even if every muscle, 
whenever it acted, had always the same amount of contraction. 
But the power of varying the amount of contraction multiplies 
the variety to an inconceivable extent. 

321. If you watch the movements of the hand with its fingers, 
as you exercise it in a great variety of motions, you can get 
some idea of its capabilities in this respect. If, too, you ob¬ 
serve its movements in different individuals in all kinds of labor 
and handiwork, you will bo still more impressed with the ex¬ 
treme variety of its movements. It is capable of performing the 
heaviest and rudest work, and at the same time the most deli¬ 
cate. How wide the difference between wielding the ax or the 
sledge-hammer, and moving the engraver’s tool in some of the 
finest productions of his art! How firm is its grasp of the 
hammer, and yet how gentle is its pressure upon the graver, as it 
moves it in almost invisible lines! The shape of the hand, with 
its fingers of unequal length, and its thumb opposite to them, 
capable of touching the tip of each of the fingers, or all of them 
together, enables it to accommodate itself to a vast variety of 
shapes and sizes of objects; and its delicate papillae, filled with 
nerves, and arranged in rows, as you can see, on the tips of the 
fingers under the skin, endow this wonderful instrument with a 
sensibility which guides its muscular movements. When, 
therefore, we consider the almost endless variety of its motions, 
the delicacy and accuracy of its sense of touch, and besides 
these, the force and grace with which it acts in the expression 
of thought and feeling, we hardly wonder that some have fixed 
upon the hand as man’s distinguishing characteristic, and we 
are impressed with the thought, that it is a fitting instrument 
of work and expression for that mind, which is the image of 
God in man. 

322. Having thus taken a survey of the muscular system, let 
as look for a moment at the whole machinery, as it works when 




220 


HUMAN PHYSIOLOGY. 


Nice adjustment of the muscular movements. How effected. 

it is engaged at the same time in some general movement, and 
in some special movements of some departments of it. Look, 
for example, at some one who is busied in conversation while he 
is walking, and is perhaps at the same time twirling something 
in different directions in his fingers. Here you have a general 
action of the muscles as described in § 318, and with it a par¬ 
ticular action of two sets of muscles in two different parts of the 
body; and yet so well do the nerves regulate these various 
movements, that there is no disturbance or confusion in the 
complicated machinery. While the muscles of the arm and 
fingers are at work executing their diversified motions, the little 
muscles of the larynx are ever varying the notes of the voice, 
and the muscles of articulation are putting that voice into every 
variety of shape. And while these movements are going on in 
these particular parts of the system, the machinery as a whole 
is executing one of its grand general movements. And besides 
all this, the muscles of respiration are at work all the while, in¬ 
troducing air into the lungs to change the blood, and forcing it 
out through the trachea to make the vocal ligaments vibrate; 
and that compound muscle the heart is pumping at the rate of 
seventy times a minute sending the blood through its tubes 
every where ; and if there be any food in the stomach, the mus¬ 
cular fibres of that organ are at work churning the food to 
make more blood. How complicated is the machinery that per¬ 
forms all these operations, and yet with what precision every mus¬ 
cle, nay, every individual fibre works in obedience to the nerves ! 

323. The question arises, how in all the diversified action of 
the muscles their nice adjustment is effected. How do the 
muscles know , as we may express it, just how much to do in 
each movement? When, for example, you reach your hand 
up to touch some object, how does each muscle know just what 
degree of contraction is necessary to make the hand go with 
precision to the particular point arrived at ? And so when one 
is playing on an instrument with the fingers, as the piano, vary¬ 
ing their pressure continually in accordance with the desired loud¬ 
ness of the sound, how does each muscle know just what amount 
of contraction is required of it in each movement ? Though the 
senses of vision and touch afford some assistance in the guidance 
of muscular action in such cases, something else is manifestly 
necessary. Sir Charles Bell, therefore, supposes that there is 
what he calls a muscular sense , which acts as a guide to th& 
muscles, in connection with the senses of sight and touch. In 
some cases it is the sole guide. On this subject, Sir Charles 




THE MUSCLES. 


221 


Sir Charles Bell’s description of the muscular sense. 

says, “ When a blind man, or a man with his eyes shut, standi 
upright, neither leaning upon or touching aught; by what 
means is it that he maintains the erect position ? The sym¬ 
metry of his body is not the cause ; the statue of the finest pro¬ 
portion must be soldered to its pedestal, or the wind will cast it 
down. How is it, then, that a man sustains the perpendicular 
posture, or inclines in due degree towards the winds that blow 
upon him ? It is obvious that he has a sense by which he 
knows the inclination of his body, and that he has a ready ap¬ 
titude to adjust it, and to correct any deviation from the per¬ 
pendicular. What sense then is this ? for he touches nothing, 
and sees nothing ; there is no organ of sense hitherto observed 
which can serve him, or in any degree aid him. Is it not that 
sense which is exhibited so early in the infant, in the fear of 
falling ? Is it not the full development of that property which 
was early shown in the struggle of the infant while it yet lay in 
the nurse’s arms ? It can only be by the adjustment of muscles 
that the limbs are stiffened, the body firmly balanced, and kept 
erect. There is no other source of knowledge, but a sense of 
the degree of exertion in his muscular frame, by which a man 
can know the position of his body and limbs, while he has no 
point of vision to direct his efforts, or the contact of any exter¬ 
nal body. In truth, we stand by so fine an exercise of this 
power, and the muscles are, from habit, directed with so much 
precision, and with an effort so slight, that we do not know 
liow we stand. But if we attempt to walk on a narrow ledge, 
or stand in a situation where we are in danger of falling, or rest 
on one foot, we become then subject to apprehension ; the actions 
of the muscles are, as it were, magnified and demonstrative of 
the degree in which they are excited.” 

324. It is obvious then that this muscular sense informs the 
mind of the changing postures of the body, and guides the 
muscles in effecting these postures. And it has a particular set 
of nervous fibres devoted to it, separate from those fibres which 
excite the muscles to action, .though they are ordinarily in¬ 
closed in the same sheath. This sense, it may also be remarked, 
is a source of pleasure, as well as the other senses. The mo¬ 
tions of the body are attended with a sense of enjoyment, which 
lightens labor, and adds zest to our active sports. The enjoy¬ 
ment of the muscular sense we see constantly exemplified in the 
gambols of animals. It may be still further remarked, that this 
sense is capable of being educated like the other senses. But 
of this I shall speak in another place. 

19* 





222 


HUMAN PHYSIOLOGY. 


All thought and feeling communicated by muscles. 


CHAPTER XIII. 

LANGUAGE OF THE MUSCLES. 

325. As the nerves of sensation are the inlets of all know¬ 
ledge to the mind, the nerves of motion are the outlets bv 
which all knowledge is communicated. Thought and feeling 
are expressed only by muscular motion. It is true that there 
are some accompanying and subordinate modes of expression, 
as the flowing of tears, the action of the capillaries producing 
blushing, and the paleness occasioned by fear. But these 
could not of themselves alone communicate thought and feel- 
ing, and can do so only by being associated with other signs. 
They only add force to the expression already produced by 
muscular action. Indeed they are signs which can not be un¬ 
derstood, unless muscular action interpret them. Thus if tears 
flow, we know not whether they are tears of joy or sorrow, ex¬ 
cept as the expression of the countenance informs us; and ex¬ 
pression, as I shall show you in this chapter, is wholly the 
result of the action of muscles. So too, the muscles of the face 
tell us, whether the blush that mantles there is the blush of 
shame, or of modesty. And when we see paleness caused by 
fear, we know that this is the cause, only from the expression 
of the countenance and the attitude of the body, which may 
very properly be called the expression of the body, though it is 
much less marked than the expression of the countenance. 

326. It is by the voice chiefly that thought and feeling are 
communicated. And every variation of note, or of articulation, 
is caused, as I shall show you in the next chapter, by the action 
of muscles. When the muscles of the hand communicate to 
others thought and feeling by writing, they merely translate 
the language of the muscles of the vocal organs into conven¬ 
tional signs. Leaving the language of these vocal muscles for 
another chapter, I shall in this notice the language of the other 
muscles of the body and especially of those of the face. 

327. As we watch an animated speaker, we see that it is not 
the face alone, that adds force to his utterances by its corres¬ 
ponding expressions. Various parts of the body in a measure 
do the same thing. The head is nodded or shaken, the shoulder 
is shrugged, the foot is stamped, and above all, the hand exe- 






THE LANGUAGE OF THE MUSCLES. 


223 


Extent of range of the language of the muscles. 


cutes a great variety of'motions, in correspondence with th« 
thoughts and feelings which the mouth utters. Sometimes too, 
the whole frame is brought into action. The gestures and the 
attitudes, which are hut gestures of the whole body, are im¬ 
portant aids to the orator in conveying his thoughts and feelings 
into the minds of his auditors. 

328. This language of the muscles is used to a greater ex¬ 
tent than we are conscious of in our ordinary intercourse. We 
are not aware how much we communicate in this way. This 
language is by no means confined to those palpable acts which 
this subject suggests at once to the mind,—the broad laugh 
of merriment; the sighing, and sobbing, and weeping of grief; 
the stamping of the foot in anger ; the pointing of the finger in 
calling attention to any particular subject; the gesture used in 
beckoning one to come to you, Ac. But it includes numerous 
little and scarcely observed motions, which in great variety 
add to the significance of the words which we utter. And in 
the case of the countenance, far more is communicated in the 
aggregate by the constant gentle play of the muscles, than by 
the broader and more palpable expressions, which are occasion¬ 
ally produced by their stronger action. The deaf mute can 
gather from the language of the muscles, as it accompanies the 
voice that he can not hear, much more information as to the 
passing conversation than one would suppose that he could. 
And the full capabilities of this language we can only learn, by 
observing to what wonderful extent the deaf and dumb can 
communicate with each other by the use of natural signs, with¬ 
out any aid from those which are artificial.* 

329. While in man the muscles of the face are the chief 
agents of expression, in other animals the very limited expres¬ 
sion of which they are capable, is chiefly effected by other parts 
of the body. For example, the dog wags his tail, the cat puts 
up her back, the game-cock spreads out his ruff of feathers on 
his head, Ac. Rage is almost the only passion which can be 
expressed by animals in the countenance. They can snarl, but 

* I wns much struck with an illustration of the great range of the language of natural 
signs, in an exhibition made many years ago by the lamented Gallaudet before the legisla¬ 
ture of Massachusetts. Previous to exhibiting the attainments of his pupils, he requested, 
that if any deaf and dumb person who had not been educated in an asylum were present, 
his friends would bring him forward, that he might show how much could be communi¬ 
cated by natural signs. A man came forward, and Mr. Gallaudet learned from him by 
natural signs alone such facts as these,—the place of his residence, the fact that his parents 
were living, the number of his brothers and of his sisters, the fact that he had seen Mr, 
G. before in a certain place, &c. Any one, it may be remarked in this connection, who 
has been engaged in teaching the deaf and dumb, and who has, therefore, become skilled 
in the use of sign-language, can converse quite readily by signs with foreigners from any 
part of the wofl. 







224 


HUMAN PHYSIOLOGY. 


Principal muscles used in smiling and laughter. 

they can not laugh or cry. Hence it has been said, that man 
can be very properly distinguished from other animals by 
calling him “ a laughing and crying animal.” 

330. Though the variety of expression in the human coun¬ 
tenance is very great, it is ordinarily produced by the action 
of very few muscles. The principal muscles are these—the 
muscle that wrinkles the eyebrow, causing frowning; the 
muscles which draw down the corners of the mouth; and 
those which draw them up. When a smile occurs, it is pro¬ 
duced by the muscles which raise the corners of the mouth. 
When sadness is expressed, it is done by the muscles by which 
the corners of the mouth are drawn down. Hence the origin 
of the common expression, “ down in the mouth.” In laughter, 
the muscles which raise the corners of the mouth act strongly, 
wrinkling the cheek, simply because the corner of the mouth is 
carried up so far as to push up the cheek before it. One other 
muscle is brought into some action—the circular muscle which 
closes the eyelids—for the eyelids are brought nearer together 
in laughter, though in mere smiling they are not. In Fig. 
126, representing broad laughter, you see the two effects 
spoken of above, the wrinkling of the upper part of the cheek, 


FIG. 126. 







THE LANGUAGE OF THE MUSCLES. 


225 


Muscles used in the expression of grief. 

and the partial closure of the eyelids. In weeping, the 
muscles that draw down the corners of the mouth, which in 
the mere expression of sadness act slightly, now act strongly. 
At the same time the frowning muscle wrinkles the eyebrow. 
In ordinary weeping it does so but slightly, but in weeping 
from pain this muscle is strongly contracted. So it is also 
when there is crossness mingled with the grief. Fig. 127, 


FIG. 127. 



which is the face of a faun weeping from pain, illustrates these 
points. Sir Charles Bell, from whose work on the Anatomy 
of Expression most of the figures in this chapter are taken, 
says that he represents the expression of weeping in the face 
of a faun, because it is mean and ludicrous as seen in the 
countenance of man. 

331. It is very commonly supposed that the eye has much 








226 


HUMAN PHYSIOLOGY. 


Prominent agency of the mouth in expression. 

to do with the expression of the countenance, and hence such 
plirases as these are in universal use—a speaking eye; a wild 
eye; the witchery of the eye; the eye flashed, &c. But the eye 
of itself has no active agency in expression. The muscles 
which move it have, but not to any great extent ordinarily 
Of them I shall speak in another part of this chapter. The 
apparent expression which the eye has is merely apparent, and 
not real. It results altogether from the position of the parts 
about the eye. This can be proved to you by any portrait 
painter. It is related of an artist that, when a royal visito. 
was admiring a sketch of the face of a weeping child, he said 
to him, “ has your majesty a mind to see how easy it is to 
make this very child laugh ?” As the king said that he should 
like to see it, the artist rubbed out a little at the corners of the 
mouth and on the eyebrows, and added a few strokes to represent 
the corners of the mouth as raised, and the eyebrows as with 
out wrinkles, and the face, which was the moment before the 
very picture of grief, now exhibited a merry laugh. Afterward 
he as readily restored the original expression. Now in this 
case there were the same eyes in the two expressions. The al¬ 
terations were made only in the neighboring parts, and the 
same eyes were apparently weeping eyes at one time and 
laughing ones at another. 

332. In Fig. 128 and 129 you can see how much the 
mouth alone affects the expression of the whole countenance. 
The apparent expression of the eye is wholly altered by the 


FIG. 128. 


FIG. 129. 













226 


HUMAN PHYSIOLOGY. 


Prominent agency of the mouth in expression. 

to do with the expression of the countenance, and hence such 
phrases as these are in universal use—a speaking eye; a wild 
eye; the witchery of the eye; the eye flashed, &c. But the eye 
of itself has no active agency in expression. The muscles 
which move it have, but not to any great extent ordinarily 
Of them I shall speak in another part of this chapter. The 
apparent expression which the eye has is merely apparent, and 
not real. It results altogether from the position of the parts 
about the eye. This can be proved to you by any portrait 
painter. It is related of an artist that, when a royal visito. 
was admiring a sketch of the face of a weeping child, he said 
to him, “ has your majesty a mind to see how easy it is to 
make this very child laugh ?” As the king said that he should 
like to see it, the artist rubbed out a little at the corners of the 
mouth and on the eyebrows, and added a few strokes to represent 
the corners of the mouth as raised, and the eyebrows as with 
out wrinkles, and the face, which was the moment before the 
very picture of grief, now exhibited a merry laugh. Afterward 
he as readily restored the original expression. Now in this 
case there were the same eyes in the two expressions. The al¬ 
terations were made only in the neighboring parts, and the 
same eyes were apparently weeping eyes at one time and 
laughing ones at another. 

332. In Fig. 128 and 129 you can see how much the 
mouth alone affects the expression of the whole countenance. 
The apparent expression of the eye is wholly altered by the 


FIG. 128. FfG. 129. 







THE LANGUAGE OF THE MUSCLES. 


227 


The eye has little active agency in expression. 

change about the mouth. If we could add at the same time 
a change at the eyebrows, the expression of the eye would be 
much more affected. 

333. The language which is ordinarily used, in relation to 
the agency of the eye in the expression of the countenance, 
implies that the eye itself, apart from any motion, changes in 
the changing expression. How this is done is not inquired; 
but there seems to be an ill defined notion that the animal 
spirits, as it is expressed, flow into the eye more or less freely 
with the changing feelings, or that a nervous influence is 
exerted in some way upon the eye, altering its appearance. 
These notions are so universal, and are so inwrought into our 
language, and especially the language of poetry, that scientific 
men even are apt to use the expressions to which they give rise, 
in their descriptions of the language of the passions. Even Sir 
C. Bell, in his celebrated book on the Anatomy of Expression, 
in describing the expression of the emotion of joy, uses the 
phrase, the eye is lively and sparkling. Let me not be under¬ 
stood to mean, that I would have the expressions, in such uni¬ 
versal use in common language and in poetry, given up. I 
would as soon claim that the expression, the sun rises, should 
be abandoned in common language. But as the astronomer 
would have it understood, that the apparent fact, that the sun 
rises, is only apparent, not real, so as a physiologist, I would 
have it understood, that the apparent active agency of the eye 
in the expression of the countenance is not real. And as it 
would be objectionable to speak of the sun as rising, in a book 
on astronomy, so in a professional book on the Anatomy of 
Expression it is objectionable, in a description of the physical 
signs of an emotion, to use the common phrases in regard to 
the agency of the eye in expression. 

334. Having thus noticed the principal muscular motions 
that are concerned in the expression of the countenance, I pro¬ 
pose now to go more extensively into the subject, and show 
you how other muscles, besides those to which I have alluded, 
act in producing certain expressions. I shall also show how 
the expressions are varied by combinations of muscular action, 
for it is as true of the muscles of expression in the face, as it 
is of the muscles generally, as stated in § 309, that almost every 
movement is produced, not by the action of one muscle alone, 
but by the action of several, sometimes many muscles. The 
various expressions of the countenance are all of them com¬ 
pound results, some of them more so than others. 





228 


HUMAN PHYSIOLOGY. 


Description of the muscles of expression in the face. 

335. I will first call your attention to the particular muscles 
of expression in the face, and indicate their inode of action. 
They are represented in Fig. 130. There is a thin flat muscle 


FIG. 130. 



MUSCLES OF THE FACE. 


covering the whole top of the head, represented at 1, 2, and 3; 
3 being its thin tendinous part. It is fastened to the large 
bones behind, and in front its fibres end in the skin of the fore¬ 
head and the eyebrows, and in the circular muscle of the eye¬ 
lids, 4. When it contracts, therefore, it raises the skin of the 
forehead and the eyebrows; and if it contract strongly, it 
wrinkles the forehead. The circular muscle of the eyelids, 4, 
when it contracts closes the eye. This and the large frontal 
muscle just described, you can see, must have much to do with 
the expression of the countenance. There is a very important 
though small muscle which is not seen on this figure. You 
see it on Fig. 113, at a. It is attached to the bone at the side 
of the top of the nose, and is inserted into the skin of the eye¬ 
brow. It is called the corrugator supercilii , or wrinkler of the 
eyebrow. From the agency which this muscle has in the ex¬ 
pression of certain passions and emotions, comes the word in 
so common use, supercilious. Though a little miiscle, it is 






THE LANGUAGE OF THE MUSCLES. 


229 


Muscles of the face continued. 

truly a supercilious one. It has, as you will see as we go on, 
a large play in many varieties of expression, produced by 
combinations of action in the muscles of the face. There are 
two muscles on the nose, 5 and 6, which compress the nose, 
and wrinkle its skin. They have some agency in certain ex¬ 
pressions of the countenance. At 7 is the circular muscle of 
the mouth. When this contracts it closes the lips, and if it 
act strongly it pushes them out. This is the muscle with which 
in part pouting is done. At 8 is a muscle which is fastened 
above to the bone of the nose, and runs down, its fibres ending 
in the wing of the nose, and in the upper lip. When it con¬ 
tracts, therefore, it moves the wing of the nose outward, and 
draws up the lip. You see this muscle in action in some 
emotions, the nostrils appearing spread out. ' At 9 is a muscle 
which raises the lip, and at 10 and 11 are two muscles, that 
raise the corner of the mouth, carrying it a little to one side. 
At 13 is the muscle which acts in opposition to the two last. 
It pulls the corner of the mouth down. At 12 is the muscle 
which pulls down the lower lip. At 18 is the muscle in the 
side of the mouth, which draws the corner of the mouth 
backward, and also serves to press the cheek inward, and thus 
prevent the food from getting outside of the teeth when we are 
chewing it. This muscle also, by its compressing power, forces 
out the air from the mouth when the cheeks are distended, as 
in blowing a horn or a trumpet. Hence it is called buccinator , 
from buccinare , to blow a trumpet. At 15 is a large muscle 
which closes the lower jaw against the upper, and although its 
chief use is to masticate the food, it has some agency in 
the expression of the countenance, in fixing the teeth firmly 
together, as in the expression of rage. There are three muscles 
which move the ear ; 19, moving it upward; 1 7, forward; 
and 21, backward. These have but little power in man, but 
in some animals they move the ear considerably, and are 
prominent agents of expression. 

336. In Fig. 131 the muscles about the mouth, which have 
so much to do with the expression of the countenance, are very 
distinctly shown. At a is the muscle which draws up the wing 
of the nose and the lip; b raises the lip; c raises the corner of 
the mouth; d and e raise the corner of the mouth, an 1 at the 
same time carry it outward; n draws it outward ; m draws it 
downward and outward in which it is assisted by a broad thin 
muscle, o, which situated just under the skin comes up from 
the neck; l draws the lower lip downward; and i is the cir- 

20 






230 


HUMAIn physiology. 

Muscles of expression about the mouth. 


FIG. 131. 



MUSCLES ABOUT THE MOUTH. 


cular muscle which closes the lips, and thrusts them out in 
pouting. At h is a short muscle which is fastened to the sockets 
of the teeth, and has its fibres ending in the skin of the chin. It 
therefore draws the chin up when it contracts. It has so much 
agency in the expression of scorn and contempt that it has been 
called the superbus. It is by the action of this muscle, together 
with the circular muscle i , that the expression termed pouting 
is produced. The muscles which I have thus described are all 
in pairs; and in every pair both muscles contract always 
exactly alike, unless affected by disease. We laugh and frown 
and weep on both sides alike. All of these muscles of ex¬ 
pression in the face are governed in their action by the 
branches of one nerve, the respiratory nerve of the face. 
When this nerve, therefore, is paralyzed on one side, and not 
on the other, as is no uncommon occurrence, these muscles on 
the paralyzed side are motionless, and the individual can laugh 
and frown and weep on only one side of the face. In Fig. 82 
you have illustrated the result of this partial paralysis, the 
face being perfectly quiescent on the left side. The contrast 
would have been still greater if the face had beeu repre¬ 
sented as in more decided action, as laughing, for example. 













THE LANGUAGE OF THE MUSCLES. 


231 


Action of particular muscles in passions and emotions. 

337. Having thus described the muscles of the face which 
are the agents of expression, I will now show their action in the 
expression of different passions and emotions. And I remark, 
that you will see, as I proceed, that so far from there being any 
one muscle devoted to the expression of one emotion or passion, 
expression is commonly the result of the combined action of 
many muscles. And you will also see that, by virtue of this 
combination, the same muscle often takes a part in the ex¬ 
pression of various emotions. 

338. When the frontal muscle (1, 2, 3, Fig. 130) contracts 
it raises the eyebrows. This motion expresses either doubt or 
surprise, and the observer determines which it is, by the ex¬ 
pression of other parts of the countenance accompanying it, or 
in other words, by the action of other muscles in the face. 
When this muscle contracts very strongly, it draws up the eye¬ 
brows so much, as to push up the skin of the forehead, and 
wrinkle it. This, as you will soon see, is one of the many mo¬ 
tions of the face which make up the expression of great bodily 
fear. In joy this muscle acts moderately, raising the eyebrow, 
therefore, but a little. This muscle often acts in connection 
with the corrugator supercilii , the wrinkler of the eyebrow. 
This may be seen in Fig. 132, respresenting a testy, peevish, 
jealous melancholy. Here the corrugator and the frontal 
muscles are both in strong action. You see also in this face 
certain muscles about the mouth acting forcibly. The muscle 
which draws the corner of the mouth down is in action while 
the superbus (A, Fig. 131,) is drawing up the chin which 
pushes up the lip before it. At the same time the muscle 
which draws up the wing of the nose and the lip, (a, Fig. 131,) 
contracts to some extent, producing an arching of the mouth, 
and a peculiar shape of the wings of the nose. The upper lip 
is arched by the action of this muscle in such a way, as to fit 
the arching upward of the lower lip, produced by the superbus 
and the muscle which draws down the corner of the mouth. 

339. In the expression just described, and illustrated by the 
figure, you see that the muscle which draws down the corner 
of the mouth has a considerable agency. Now, this muscle is 
the chief agent in the expression of sorrow, as you saw in the 
first part of this chapter The difference in the two cases lies 
in the combination of action of the muscles. Thus, in sorrow 
the muscle which draws down the corner of the mouth, does 
not have the superbus to act with it, as in the case of the 
passion, or rather cbmpound feeling, represented r: Fig. 132. 







232 


HUMAN PHYSIOLOGY. 


Action of the muscles in fretful melancholy. 


FIG. 132. 



So also, in some forms of grief the corrugator supercilii acts 
quite strongly, as seen in Fig. 127, where the grief is repre¬ 
sented as caused by bodily pain. It performs a different office 
in this case from what it does in the case of the expression re¬ 
presented by Fig. 132, simply through the accompanying action 
of other muscles, thus illustrating the effect of combination in 
muscular action in varying the character of the expression. I 
have already alluded to the different degrees of action in this 
muscle in different forms of grief in § 330. In quiet sorrow 
this muscle is not in action, but there is a general languor re¬ 
laxing the muscles of the face, while the corners of the mouth 










THE LANGUAGE OF THE MUSCLES. 


283 


Action of the muscles in calm pleasure, and in admiration. 

are slightly depressed. It is a state of the muscles directly op¬ 
posite to that which exists when there is a calm quiet pleasure.. 
Tlieu most of the muscles are in a state of gentle action, and 
the corners of the mouth are a little raised, giving the radiance 
of a light smile to the whole countenance. The frontal 
muscle, slightly raising the eyebrows, adds to the effect. 

340. The attitude, for so we may call it, of the countenance 
in admiration, is quite nearly allied to that which I have just 
described. The brow is expanded by the action of the frontal 
muscle, and there is a slight smile produced by the raising of 
the corners of the mouth. But the expression differs in some 
respects from that of mere pleasure. The frontal muscle acts 
rather more strongly in the former than in the latter, the eye 
is more wide open, and is fixed upon the object of the admira¬ 
tion, and the mouth is apt to be open, the jaw falling a little, 
so that we can see the edge of the lower teeth and the tip of the 
tongue. In both pleasure and admiration the expression varies 
much in different individuals, according to their temperaments, 
being characterized by activity in some, and in others more by 
relaxation or even languor. 

341. Let me now call your attention to an expression of the 
countenance, in which many of the muscles are in a state of 
strong action. I refer to the expression of rage represented in 
Fig. 133. The combination of muscular action here is quite 
extensive. The corrugator supercilii acts forcibly, but un¬ 
steadily, as is the case with the action of all the muscles in the 
expression of this passion. The frontal muscle acts at the same 
time, raising the eyebrows. The eyes are opened widely, 
showing the rolling eyeballs. The muscle that raises the upper 
lip, 6, Fig. 131, and the muscle that raises the wing of the 
nose and the lip, are in strong action. The nostrils are there¬ 
fore spread out to the utmost, and the upper lip is drawn up¬ 
ward. But as the circular muscle of the mouth also acts 
strongly, there is only that part of the upper lip to which 
the muscles, a and b , Fig. 131, are attached, that can be drawn 
up. This point is just where the sharp eye-teeth, or canine 
teeth, as they are sometimes called, are situated. They are 
therefore seen laid bare. This allies man to the snarling 
brute, that shows his sharp teeth in his rage. Cooke, the tra¬ 
gedian, is said to have had great power in the use of these 
muscles. “In him,” says Sir Charles Bell, “the ringentes (the 
snarling muscles) prevailed; and what determined hate could 
he express, when, combined with the oblique cast of his eyes, 






234 


HUMAN PHYSIOLOGY. 


Complicated muscular action in expressing rage. 


FIG. 133. 



he drew up the outer part of the upper lip, and disclosed a 
sharp angular tooth !” In rage the teeth are firmly closed by 
the muscles which move the lower jaw, and when utterance is 
given to it by the voice, these muscles but slightly relax to let 
the words out through the almost closed teeth, and are rigid 
again as soon as the words are finished. 

342. The expression of mere bodily fear, represented in Fig. 
134, is very different from that of rage, although some of the 
muscles act in the same way in both. The frontal muscle acts 
very forcibly, raising the eyebrows to their utmost extent, and 
the eyeballs are largely uncovered, giving to the eyes a broad 
stare. The corrugator supercilii is perfectly relaxed, while in 
rage it is strongly contracted. The lip is raised and the nos¬ 
trils are spread out by the same muscles, a and b. Fig. 131, 
which act so forcibly in rage. But the circular muscle of the 
mouth, t, is relaxed, so that the whole lip is raised, instead of 




THE LANGUAGE OF THE MUSCLES. 


235 


Movements of the eye in expression. 


FIG. 134. 



a part of it, as is the case when rage is expressed. The lower 
jaw is fallen, while in rage it is in the opposite condition. The 
hair is raised up by a general action of the whole frontal 
muscle, 1, 2, 3, in Fig. 130. 

343. The muscles of the eye, that is, those which move the 
eyeball have some agency in certain expressions of the counte¬ 
nance. Thus, in admiration, the fixing of the eye upon the ad¬ 
mired object makes a part of the expression. In the expression 
of devotion the eye turns instinctively upward. There are cer¬ 
tain involuntary motions of the eyeball, which have much to 
do with expression in certain states of the body, and in certain 
emotions. These motions are performed by the oblique mus¬ 
cles (§ 307.) When the straight muscles which ordinarily con¬ 
trol the motions of the eye lose their power from a state of 
general insensibility, the eye is given over to the action of 
these oblique muscles, which are involuntary, and therefore is 





236 


HUMAN PHYSIOLOGY. 


Muscles of expression peculiar to man. 

rolled about in its socket, being turned upward all the time, so 
that the white of the eye only is seen. This occurs in sleep, in 
fainting, in the stupor of disease, and in the approach of death. 

344. The loss of power in the voluntary muscles of the eyeball 
and eyelid is often seen ludicrously exhibited in the intoxicated 
man. He squints and sees double from deficiency of action in 
the straight muscles of the eyeball. The oblique involuntary 
muscles of course roll the eye in proportion to the deficie ncy of 
these straight muscles. The voluntary muscle too, which holds 
up the upper lid, fails to do its duty, and the lid is constantly 
disposed to fall over the eye. The frontal muscle is therefore 
called upon to aid it. Hence, in the effort of the drunkard to 
keep his eyes open, you see him raise up the eyebrows, the 
eyelids being of course dragged up after them to a little extent. 
“ It is,” says Sir Charles Bell, “ the struggle of the drunkard to 
resist, with his half-conscious efforts, the rapid turning up of the 
eye, and to preserve it under the control of the voluntary 
muscles, that makes him see objects distorted, and strive, by 
arching his eyebrows, to keep the upper lid from descending. 
The puzzled appearance which this gives rise to, along with the 
relaxation of the lower part of the face, and the slight paralytic 
obliquity of the mouth, complete the degrading expression.” 

345. I have thus pointed out the agency of the several mus¬ 
cles that are engaged in the expression of the countenance. 
Most of them are peculiar to man, being found in no other 
animal. The inferior animals are variously endowed in regard 
to muscles of expression. But even those that have the most 
expression, have but few of those muscles which we find in the 
face of man devoted to this purpose. They have the muscles 
that move the eyes, those which raise the upper lip and thus 
expose the teeth, and to some extent those which distend the 
nostrils. The horse is especially endowed in regard to this 
latter motion. In that glowing and beautiful description of the 
horse in Job it is said, “the glory of his nostrils is terrible.” 
But most animals, even of the higher orders, have but a limited 
motion of the nostrils compared with man. In him they have 
much more to do with the expression of the countenance than 
is commonly supposed. Their chief agency is in the expression 
of the nobler passions, and Sir Charles Bell remarks, that the 
great tragedians, Mrs. Siddons and Mr. John Kemble, exhibited 
their power in this respect in a remarkable manner. 

346. None of the inferior animals have the corrugator super - 
cilii. Indeed they have no eyebrows to move. The eyebrow 






THE LANGUAGE OF THE MUSCLES. 


237 


Muscles of expression in animals. 

is a strong peculiarity of man, and in view of its agency in the 
expression of the countenance, varied as it is by the frontal mus- 
cle and the corrugator, it has been said by some one, that it is 
“ the rainbow of peace, or the bended bow of discord.” So also, 
the muscles that raise and depress the corners of the mouth 
are wholly peculiar to man. It is sometimes said that the dog 
smiles. But if you observe him closely, you will see that as he 
separates his lips or opens his mouth, at the same time that he 
wags his tail, there is no raising of the corners of the mouth, 
and therefore no true smiling. The idea that he smiles has 
come from mere association with other motions by which he indi¬ 
cates pleasure. The same can be said of the expression of sorrow 
in the dog and other animals. There is little of it in the face 
itself, amounting to nothing more than a mere downcast look, 
If even that; and we connect the idea of sorrow with the face, 
by the force of association, from hearing the cries and witness¬ 
ing the movements which distress produces. The grand peculi¬ 
arities of human expression are in the muscles whose action I 
have noticed in this paragraph, viz., the muscle that wrinkles the 
eyebrow, the muscle that raises it, and those muscles which 
move the corners of the mouth up and down. No animal but 
man can frown, or weep, or laugh, for it has not the muscles by 
which these acts are done. 

347. Fear and rage are almost the only passions that are 
expressed in the faces of animals. And in some of them there 
are special provisions in muscular endowment, for the expression 
of these mere brutal passions, particularly for rage. Thus, in 
beasts of prey the ringentes, or snarling muscles have great 
power. They raise the lip strongly, and display the sharp long 
teeth which are to rend their prey in pieces. The eye too is 
made terrible by certain muscles which are not found in man. 
They are muscles which draw the eyelids backward upon the 
prominent eyeball, thus producing a fixed staring of the eye, 
and exposing its brilliant white coat, which by reflecting the 
light gives the eye a sparkling appearance. These muscles Sir 
Charles Bell calls scintillantes , from the apparent scintillating 
effect which they produce. In the cat tribe light is reflected 
from the bottom of the eye, when the pupil is dilated so as to 
admit the light over a large portion of the retina. This occurs 
in an obscure light simply because the pupil is then so much 
dilated. The light is not created in the eye, and it is no indi¬ 
cation of passion, as has been supposed. 

348. You have seen the fact most fully illustrated in this 






238 


HUMAN PHYSIOLOGY. 


Variety of combination in muscular action in expression. 

chapter, that it is from combinations of action among the mus¬ 
cles, that the various expressions of the countenance result. 
To produce each one of these combinations, there must be a 
consent of action between the muscles. Some are relaxed, while 
others are contracted; and those which are contracted are in 
different degrees of contraction. Sometimes this harmony of 
action is sportively destroyed by one who has great command 
over the muscles of the face, and the most incongruous expres¬ 
sions result, mingled together in the same countenance, giving 
it a very ludicrous appearance. And I may remark, that the 
portrait painter is not always true to nature, but sometimes fails 
to depict the full harmony of muscular action in the expression 
of the countenance. I have noticed some of the combinations 
of muscular action in expression; but the view which you thus 
get of them gives you but a faint idea of the infinite variety 
of expression of which the human countenance is capable, as the 
result of these combinations. In order to obtain some adequate 
idea of this variety, keeping the views presented in this chapter 
in your mind, watch some one engaged in speaking or in conver¬ 
sation, in whom the play of the muscles of expression is peculi¬ 
arly free. By so doing you will acquire new views of the capa¬ 
bilities of the countenance in communicating thought and feeling, 
and you will learn a lesson in this respect which the deaf mute 
from necessity learns every day. 

349. But we do not get a full view of the combination of 
muscular action in expression, if we confine our observations to 
the countenance. As I remarked in the first part of this chap¬ 
ter, the muscles of other parts of the body, and sometimes of 
the whole frame, are brought into action in connection with the 
muscles of the face, in expressing thought and feeling. The 
attitudes and motions of other parts of the body correspond 
with the attitudes and motions of the countenance, so as to 
produce an harmonious effect. The hand is more used than 
any other part in aid of the countenance in expression; but the 
whole body is often brought more or less into action. The 
character of a passion can sometimes be inferred from the atti¬ 
tude merely, or from the mode of walking, as you see one at a 
distance. 


“You may sometimes trace, 

A feeling in each footstep, as disclosed, 

By Sallust in his Cataline, who, chased 
By all the demons of all passions, showed 
Their work even by the way in which he trode,” 





THE LANGUAGE OF THE MUSCLES. 


289 


Action of the respiratory muscles and the circulation in expression. 

350. But it is the muscles of the respiratory organs which 
sympathize most with the muscles of the face in expression. 
This sympathy is the result of a nervous connection, and the 
nerve of expression in the face is therefore, as before stated, 
sometimes called the respiratory nerve of the face. Observe the 
prominent agency which the muscles of the chest have in the 
decided expression of the passions and feelings. In laughing 
the individual draws in a full breath, and then lets it out in 
short interrupted jets, the muscles of the throat, neck and chest, 
especially the diaphragm, being convulsively agitated. And if 
the laughter be strong and continued, he holds his sides, which 
become really sore, from the violent action of the respiratory 
muscles in this expression of his emotions. In weeping too, 
these same muscles are affected. The diaphragm acts spasmod¬ 
ically, the breathing is cut short by sobbing, the inspiration is 
quick, and the expiration is slow, and often with a melancholy 
note. But it is not alone in these marked cases that the respi- 
atory muscles are seen to act, but you can observe their action 
in many of the slighter expressions of feeling. 

351. There are certain effects produced by emotions upon 
the circulation, which heighten the expression resulting from 
muscular action. I have already referred to the blush of mod¬ 
esty, and the paleness of fear. In both laughter and weeping 
the spasmodic action of the muscles of respiration impedes the 
flow of blood through the lungs; and hence the countenance 
becomes flushed or suffused with the blood of the impeded cir¬ 
culation. This is very different from common blushing, which 
has nothing to do with the state of the general circulation, but 
is entirely a local effect, confined to the capillaries of the part, 
where it occurs. These capillaries are affected by the emotion 
through nervous connections, just as the minute secreting vessels 
in the tear glands are excited to unusual action. 

352. From the views which I have presented of the capabil¬ 
ities of the human countenance in expression, you must be as 
much struck with its adaptation to the mind that moves it, as 
you were with the hand in this respect. Both are instruments 
of the mind, by which it accomplishes its purposes; and they 
would be out of place in any other animal, even one of a higher 
order, because he has not a mind capable of using such instru¬ 
ments to advantage. Man needs the face, with all its endow¬ 
ments, to express his thoughts and feelings, and the hand to do 
the handiwork which his mind designs; and the Creator has 




240 


HUMAN PHYSIOLOGY. 


Training of the muscles of expression. Beauty depends much on their action. 


proportioned the capabilities of these instruments to the necesi- 
ties and the mental powers of man. 

353. As the muscles of the face perform such high functions, 
as the instruments of the mind in expression, it is important 
that they should be well trained in these functions. Much is 
often said about the importance of grace in the attitudes and 
movements of the body, while seldom is a thought given to the 
attitudes and movements of the countenance. Muscles are at 
work in the one case as well as in the other, and the muscles 
of the face can be trained to work skillfully and gracefully as 
well as the muscles of any other part of the body. Indeed, 
grace of action is much more important in the face than in the 
body generally, because the muscles there are used so much 
more for expression than in any other part. And yet the 
speaker, who aims to gesture gracefully with his arms, is often 
very careless in regard to the gestures, for so we may call them, 
which are made by his face. So too the parent, who takes 
unwearied pains to make the gait and attitudes of her child grace¬ 
ful, often allows most uncouth attitudes of countenance to grow 
into a habit. Many a child that has been drilled most faithfully, 
in order to overcome awkwardness of movement, is suffered to 
become incurably awkward in the face, as some one has aptly 
expressed it. Sometimes even a habit of making grimaces is 
unconsciously contracted, which utterly prevents the countenance 
from accompanying the words that are uttered with any thing 
like appropriate expression. 

354. Beauty depends much upon the attitudes and move¬ 
ments of the face, and not alone upon the shape of the features. 
We often see a face which is beautiful in repose, that becomes 
ugly the moment that it is in action, because the movements of 
the muscles are so ungainly. And, on the other hand, we often 
see faces which are quite at fault in the shape of the features, 
display great beauty when in action, from the movements which 
play so easily and gracefully among the muscles. It is a great 
triumph of the spiritual over the physical, when the mind within 
thus puts its impress of beauty upon a material form which is 
destitute of symmetry. When it does this, there is more to 
challenge our admiration, than when the sculptor chisels the 
marble into beauty. And if he were to undertake, in imitation 
of what we often see in living nature, to put beauty into ill- 
shapen features, he would signally fail. This can be done only 
by the active mind within, moving plastic features by the subtle 
agency of nerves and muscles. In relation to the inadequacy 




THE LANGUAGE OF THE MUSCLES. 


241 


Skill in the use of the muscles of expression. 

of mere symmetry of form to meet our ideas of beauty in the 
living countenance, Addison has justly said, “ No woman can 
be handsome by the force of features alone, any more than she 
can be witty only by the help of speech.” 

355. There is nearly as much difference in skill in the use of 
the muscles of the face, as in the use of those of the hand. And 
we need not go to the accomplished orator or actor, as furnish¬ 
ing us alone with the higher examples of this skill. It is often 
seen exhibited in the ordinary intercourse of life, in those who 
have great capacity of expression, together with a mind uncom¬ 
monly refined and susceptible. In them every shade of thought 
and feeling is clearly and beautifully traced in the countenance. 
While this is the result of education of the muscles of expres¬ 
sion, an education of which the individual is for the most part 
unconscious, no direct attempt in the training of these muscles 
will succeed, unless the mind itself be of the right character. 
Intelligence and kindness cannot be made to beam from the 
countenance, if they do not exist in the moving spirit within. 
They are often awkwardly counterfeited, the one by the bustling 
air assumed by the face of the shallow pretender, and the other 
by the smirk of him who smiles only to get favor or profit from 
others. The counterfeit is often mistaken for the reality ; and 
in relation to the truly intelligent and kind, there is often much 
error in the estimate put upon their intelligence and kindness, 
from the different degrees in which these qualities, when exist¬ 
ing in the same amounts, are exhibited in the expression of the 
countenance. In some, the muscles of expression respond more 
readily and aptly to the thought and feeling within, than they 
do in others. 

356. I know not of any more beautiful and striking exempli¬ 
fication of the influence of the mind and heart upon the expres¬ 
sion of the countenance, than is to be seen in those institutions 
where juvenile outcasts from society are redeemed from their 
degradation by the hand of benevolence. You can often note 
most clearly the progress of the mental and moral cultivation 
in the lineaments of the face, as lively intelligence takes the 
place of stolid indifference, and refined sentiment that of brutal 
passion. Sometimes a few weeks suffice to change the whole 
character of the expression. The dull eye becomes bright, not 
from any change in the eye itself, but from the intelligence and 
sentiment which now play upon the muscles in its neighborhood. 
Those muscles which impart a lively and pleasant cast to the 
countenance when they are in action, are awakened from their 

• 21 




242 


HUMAN PHYSIOLOGY. 


The habitual expression of the countenance after death. 

long continued dormant state by the magic wand of benevolence, 
and thus give outward expression to the thoughts and feelings, 
which genial influences are producing in the mind and the heart. 
The change is often as great in a little time, as it would be in 
the face of an idiot, if he could be suddenly brought into the 
full possession of the mental faculties. 

357. The habitual expression of the countenance, depending 
as it does upon the habitual condition of the muscles, is seen 
after death. In the state of relaxation which immediately 
occurs at death the face is very inexpressive, because its muscles 
are, together with those of the whole body, so entirely relaxed. 
But very soon they begin to contract, and they assume that 
degree of contraction to which they were habituated during 
life, and therefore give to the countenance its habitual expres¬ 
sion. It is when this has taken place—when the muscles, recov¬ 
ering from the relaxation of the death-hour, resume their accus¬ 
tomed attitude, as we may express it, that the countenance of 
our friends appears so natural to us, and we are held, as if by a 
charm, gazing upon the intelligence and affection beaming there 
amid the awful stillness of death, till it seems as if those lips 
must have language. And this expression is retained through 
all the period of rigidity, till it is dissolved by the relaxation 
which succeeds this state and ushers in the process of decay. 
It is thus that the soul, as it takes its flight, leaves its impress 
upon the noblest part of its tabernacle of flesh; and it is not 
effaced till the last vestige of life is gone, and the laws of dead 
matter take possession of the body. The state of countenance 
which I have described is thus beautifully alluded to by Byron. 
He who hath bent him o’er the dead, 

Ere the first day of death has fled, 

The first dark day of nothingness, 

The last of danger and distress, 

(Before decay’s effacing fingers 

Have swept the lines where beauty lingers), 

And mark’d the mild angelic air, 

The rapture of repose that’s there, 

The fix’d yet tender traits that streak 
The languor of the placid cheek, 

And—but for that sad, shrouded eye, 

That fires not, wins not, weeps not, now, 

And but for that chill, changeless brow, 

Where cold obstruction’s apathy 
Appals the gazing mourner’s heart, 

As if to him it could impart 

The doom he dreads yet dwells upon; 

Yes, but for these, and these alone, 




THE VOICE. 


243 


Superiority of the vocal apparatus to musical instruments. 

Some moments, aye, one treacherous hour, 

He still might doubt the tyrant’s power; 

So fair, so calm, so softly sealed, 

The first, last look by death revealed! 


CHAPTER XIV. 

THE VOICE. 

358. The apparatus of the voice is truly a musical instru¬ 
ment. We can see therefore, in its construction and arrange¬ 
ment, the application of those principles, which usually regulate 
the production of musical sounds, and which man observes in 
making the various instruments which his ingenuity has invented 
to delight the ear. It is, however, a much more perfect instru¬ 
ment than any which man has invented. Almost every musical 
instrument, it is true, has a greater compass than that of the 
human voice; but it is by no means the chief excellence of an 
instrument that it can command a great extent of the scale. 
The apparatus of the voice can execute enough of the scale for 
all common purposes. It is wonderful that its compass is so 
great as it is, for it is a very small instrument, occupying a space 
of less than an inch square where the vibrating ligaments are 
situated. In every respect besides compass this instrument far 
excels all others. Listen to a good voice which has been 
well educated. Its transitions have an ease and a grace which 
the workmanship of man can not equal; the richness and sweet¬ 
ness of its tones are above all imitation with the most perfect 
instruments; and utterance is given to its various notes with so 
little apparent effort, with so little show of machinery, in com¬ 
parison with the instruments made by man, that we are filled 
with wonder at the effects produced by so simple, delicate, and 
beautiful a piece of mechanism. But the most important cir¬ 
cumstance to be noticed is, that there are parts connected with 
this apparatus, which give articulation to the voice as it 
comes from the vocal chords, thus making it the principal me¬ 
dium of communication between man and man. This distin¬ 
guishes it from every other musical instrument, and constitutes 





244 


HUMAN PHYSIOLOGY. 


Voice of conversation and song. Voices of the brute creation. 

its crowning excellence. When I come to speak particularly 
of the articulation of the voice, you will see how really compli¬ 
cated is the apparently simple mechanism that produces the 
varied articulations, and thus makes the voice the chief medium 
of mental communication. And if you try to measure, with 
the utmost stretch of conception, the endless variety of thought 
and feeling, which this apparatus conveys daily, hourly, every 
moment from heart to heart in the intercourse of life, you will 
be able to estimate in some good degree the value of those or¬ 
gans, which, though we seldom spend a thought upon them, are 
so constantly ministering to our enjoyment. 

359. Such being the high uses for which the voice is designed, 
when it possesses a rich and flowing melody, and its articulation 
is graceful and easy, its powers of fascination are wonderful. 
Such a voice is a fit medium of communication for “ thoughts 
that breathe and words that burn.” This is more often true of 
the voice of conversation than that of song. It is in the hourly 
intercourse of life that melody of voice is most valuable to us as 
a source of enjoyment, and here its influence is often astonishing. 
It will sometimes give a charm, not to say beauty, to an ordinary 
face ; while on the other hand, the fascination of beauty is often 
destroyed by the utterance of a voice harsh and without melody. 
And it may be remarked that a rich and finely modulated voice 
of conversation, and a melodious voice of song, do not always 
go together. The voice which has delighted the ear of multi¬ 
tudes at the public concert, may be divested of all its charms, 
when used in conversation; and on the other hand, there are 
many who sing unskillfully, and yet in conversation give utter¬ 
ance to genuine and varied melody. 

360. There is music not only in the human voice, but in the 
voices also of the brute creation. And the varied forms of the 
apparatus by which it is produced show the impress of the same 
power. What variety there is in the sounds which come from 
the multitudes of different animals on our globe, and how diversi¬ 
fied is the handiwork exhibited in their vocal organs ! The pow¬ 
er from which springs this endless variety is the same as that 
which gives such diversity to the human countenance, and I 
know not which is the most wonderful display of it. And it 
may be remarked, that although the voices of some animals are 
harsh and discordant, those which we most frequently hear are 
melodious. Even some of those which are unpleasant to the 
ear, become in some degree pleasant when occasionally heard 
at the right time and in the right place, from the addition which 





THE VOICE. 


245 


Two kinds of wind instruments—reed, and those having an inflexible mouthpiece. 

they make to the variety of sounds that we hear, and from the 
associations which become connected with them. A goose on a 
common, says Cowper, is no bad performer. 

With these preliminary remarks I proceed to the investiga¬ 
tion of the subject. I shall speak first of the voice as it is pro¬ 
duced in the larynx by the vibration of the vocal chords or 
ligaments, and then treat of the articulation of the voice. 

361. As the apparatus of the voice is really a wind instru¬ 
ment, I will first develope the principles on which wind instru¬ 
ments produce the various musical notes, and 
then show you the resemblance between these lo. 135 . 

instruments and the set of organs which are j 

engaged in producing the notes of the voice. 

Wind instruments are of two kinds—those 
that have an inflexible mouthpiece, and those 
in which the sounds are produced by a vibrat¬ 
ing reed. The horn, trombone, trumpet, flute, 
fife, flageolet, flute-stop and other stops of the 
organ, &c., are instruments of the first kind. 

The cause of the variation of notes produced 
in these instruments may be thus explained. 

The column of air contained in the tube is the 
vibrating body from which proceeds the sound. 

Any thing then that affects the column of air 
affects the note. The length, the breadth, 
and the mode of producing the vibrations are 
the causes of the variation of the note. The 
holes which are in the side of a flute are for 
the purpose of altering the length of the con¬ 
fined column of air. In the trombone this is 
done by sliding one part of the instrument 
upon the other. The general rule is, the 
longer is the column of air the more grave is 
the note. Thus in the flute, the lowest note 
that can be produced by the instrument is 
made by covering all the holes, so that you 
have a column of confined air the whole length 
of the tube. The highest note, on the other 
hand, which the instrument is capable of pro¬ 
ducing is made by so arranging the fingers as 
to allow the air to escape at the first hole. 

In this case the length of the confined vibra¬ 
ting column of air extends only from the mouth 

21 * 
















246 


HUMAN PHYSIOLOGY. 


Size and width of vibrating column of air affecting the note. 

hole to the hole from which the air escapes. I take another 
illustration from the organ. Fig. 135 is a representation of one 
of the pipes of the flute-stop of the organ, which is a wooden 
box, made very much after the manner of a boy’s chesnut 
whistle. At a is the passage for the introduction of the air ; b 
is the inclosed column of air, the vibration of which produces 
the sound ; c is the place of escape for the air; and d is a mov¬ 
able plug, by means of which the vibrating column of air can 
be made longer or shorter, according to the note desired. In 
tuning the organ, if the pipe gives too low a note the plug is 
moved downward, thus shortening the column of inclosed air, 
but if too high a note, the plug is raised up. 

362. The same rule applies to the width of the vibrating 
column of air. The wider the column the graver the note, and 
vice versa. I would observe, that in a long, slender column of 
air, as in the trombone, by giving the current of air from the 
mouth a great velocity a high note may be produced ; but 
where, as in the ophicleide, the column is both wide and long, 
it is difficult to do this, because it is difficult to produce a quick 
vibration in so large a body of air, with all the suddenness and 
force with which we can move it. 

363. In those instruments which have no expedient for alter¬ 
ing the length of the column of air, such as the common horn, 
the various notes are produced by narrowing or widening the 
orifice by the agency of the lips, as the case requires, at the 
same time giving, by the varied velocity with which the air is 
forced into the instrument, a quicker or slower vibration to the 
air. Grave sounds are produced by a wide, and acute by a 
narrow opening. In playing the flute the opening of the lips 
is thus varied in order to produce a vibration which shall cor¬ 
respond with the length of the column of air. If the flute 
player, with his fingers arranged for a high note, should blow 
into the mouth hole with his lips forming a large orifice, he 
Would not produce the desired note. To produce the proper 
vibration in a short column of air, the orifice from which the air 
issues to move this column must be small enough to corres¬ 
pond, and with it there must be the requisite velocity in the air 
as it comes from the mouth. You have a good illustration of 
the influence of size of orifice on the note of sound in common 
whistling. The higher the note produced the more narrow is 
the outlet from the mouth. The size of it is regulated by both 
3he lips and the tongue. 

364. In reed instruments the variations in note are produced 




THE VOICE. 


247 


Reed instruments. Principles. Tube connected with the reed. 

in a different manner. The clarionet, hautboy, bassoon, the 
reed stops in the organ, &c., are instruments of this sort. It is 
the vibration of the thin plate called the reed that causes the 
sound. The longer this plate is, the slower are the vibrations, 
and therefore the graver is the note, and vice versa. The prin¬ 
ciple can be well illustrated in the reed stops of the organ. The 
reeds in the different pipes are made of different lengths, accord¬ 
ing to the notes which they are to produce. In a reed instru¬ 
ment played by the mouth, as the clarionet for example, the 
rapidity of the vibrations is regulated by the pressure of the lips. 
In producing a high note the lips press firmly on the reed and 
leave but a small portion of it to vibrate; while in producing a 
low note the lips press less firmly on the reed, and leave a large 
portion of it to vibrate. 

365. You see that the same principles apply to the reed as 
to the column of air in the other kind of wind instruments. In 
both cases the longer and thicker the vibrating body the coarser 
is the vibration, and the graver the note. This same principle 
also applies to stringed instruments. Thus in the piano, the 
grave notes come from long and large strings, while the higher 
notes come from slender and short ones. In the violin the 
strings are all of the same length, the larger strings giving the 
graver notes, and the smaller the higher ones. The notes are 
varied also in the case of each string, by varying the tension. 
They are varied too while playing on the instrument by varying 
the length of the vibrating strings by the pressure of the fingers. 

366. The reed is always connected with a tube. Has this 
any influence upon the note produced by the reed ? It contains 
a column of air through which the sound caused by the vibra¬ 
tion of the reed must pass. Unless, then, the vibration of this 
column of air corresponds with the vibration of the reed, it will 
alter the note. It does alter the note to some extent always. 
It never raises it, but always makes it more grave. That is, 
the vibration, in passing from the reed to the column of air, 
becomes less rapid and coarser, as is always the case when vi¬ 
bration passes from any substance to another. But the tube is 
so arranged that there may be as little change in this respect 
as possible, and yet have the combined effect of a reed and wind 
instrument secured. Holes are therefore properly placed in the 
side of the tube, so that with the fingers the column of confined 
air may, in the case of every note, be placed in correspondence 
with the vibration of the reed. Suppose the tube to be long 
and without holes; in this case low notes could be easily pro- 





248 


HUMAN PHYSIOLOGY. 


Description of the organ of the voice. Hyoid bone. Larynx. Trachea. 

duced, but attempt a high note and you would fail. The reason 
is obvious. The low note is caused by a low and coarse vibra¬ 
tion of the reed, for the transmission of which a long column 
of air is fitted. But if a high note be attempted, the slow 
vibration of the long column of air disagrees with the quick 
vibration of the reed, and flattens very much the sound after it 
comes from the reed, as it passes through the tube. As I have 
already hinted, the object of the tube is to secure in the instru¬ 
ment the combined effect of a reed and a wind instrument. 
The tube makes the reed speak, as it is expressed; that is, it 
gives intensity and an agreeable character to the sound. If 
you disconnect the reed of the hautboy or bassoon, for example, 
from its tube, and blow upon it, you can produce all the variety 
of notes, but the sound is disagreeable; but by connecting the 
tube with the reed you produce a compound sound, as we may 
call it, which has a sweet and rich melody. 

We will now examine the apparatus of the voice, and see how 
far the principles which I have developed in relation to common 
musical instruments are applicable to this instrument. 

367. Just at the root of the tongue, as described in the Chap¬ 
ter on the Bones, § 282, is a small bone, shaped so much like 
the Greek letter v that it is called the hyoid or U-like bone. 
The round end of this bone is towards the root of the tongue, 
and its two ends point backward toward the pharynx. To 
this bone is connected a long cartilaginous tube extending to 
the lungs, called the trachea, or windpipe. It is through this 
tube, as you have already learned, that the air goes back and 
forth from the lungs in respiration and speech. It is not one 
solid tube, but is composed of a great number of rings of carti¬ 
lage connected together by membranous parts. The rings are 
not perfect circles. They are deficient behind, and this deficiency 
is supplied by a membrane. The object of this arrangement is 
evident. The part of the tube where the rings are deficient is 
directly in front in its whole length of the oesophagus or gullet, 
the tube through which the food passes. If the rings had been 
made entire, it is manifest that their pressure would interfere 
somewhat with swallowing. But it is the upper part of the 
windpipe, that part which is immediately below the U-like bone, 
which claims our attention as the seat of the formation of the 
voice. This part is called the larnyx. It is formed of five car¬ 
tilages, the arrangement of which I will now show you. The 
largest of these cartilages, the one which forms the most of the 
body of this music-box, as we may call it, is the thyroid. It is 




THE VOICE. 


249 


Thyroid, cricoid and arytenoid cartilages. 


the pomum Adami , or Adam’s apple, which is so easily felt in 
the top of the neck. This cartilage forms the front and sides 
of the larynx, but it is open behind. The cricoid cartilage is 
shaped very much like a seal ring, and this resemblance gives 
it its name. The narrow part of it is situated directly under 
the thyroid cartilage, in its front and at its sides, but the broad, 
seal-like part of it is behind, projecting upward and filling up a 
part of the open space left by the deficiency of the thyroid in 
in its rear. A side view of these parts 
is given in Fig. 136, in which 1 is the 
the U-like bone; 4 is the thyroid car¬ 
tilage; and 6 the cricoid. At 8 is 
the back part of the cricoid, filling up 
a part of the space in the open rear 
of the thyroid; 3 is a horn shaped 
projection of the thyroid, and 5 is a 
smaller one below, projecting over on 
to the outside of the cricoid; 2 is a 
strong membrane or ligament connect¬ 
ing the hyoid or U-like bone with 
the top of the thyroid; 9 is the epi¬ 
glottis, drawn up by a hook ; and at 
7 are the rings of the trachea. The 
epiglottis is composed in part of car¬ 
tilage. It is, as I have already told 
you, in the Chapter on Digestion, § 78, 
the lid of the music box, the larynx, 
shutting down when we swallow, so 
that the food or drink may pass over 
it, and being raised up when we 
breathe or speak. 

368. There are two small cartilages which are not seen in 
this figure, called arytenoid cartilages, from two Greek words, 
meaning ladle and shape , because they bear some resemblance 
in form°to a ladle. They stand in the open space in the rear 
part of the thyroid, on the top of the cricoid cartilage. They 
are the pillars to which the vocal chords or ligaments are attached 
behind. These two cartilages are movable, having a regular 
joint with the upper edge of the cricoid. There are small mus¬ 
cles which pull them in different directions, and thus change 
the degree of tension and the position of the vocal ligaments, 
and of bourse vary the note of the sound produced by their vibra¬ 
tion. That you may understand how this is done, I give you 


FIG. 136. 



Side view of 

THE LARYNX. 





250 


HUMAN - PHYSIOLOGY. 


Vocal ligaments. Mode of their action. 

in Fig. 137 a diagram showing the arrangement of these liga¬ 
ments. It represents a view of them as you look down into 
the larynx, in which a is the front of the thyroid cartilage, and bb 
are the two arytenoid cartilages. To 
these you see are attached two sheets 
of membrane, which are also fastened 
all around to the inside of the thy¬ 
roid. If these movable posts, as we 
may call them, to which the ligaments 
are thus attached, be drawn back¬ 
ward, it is obvious that it will make 
the ligaments more tense. If they 
are separated from each other, the 
opening between the ligaments will 
be widened. If they are brought 
nearer together, this opening will be 
narrowed, and the forward part of the free edge of each liga¬ 
ment will be prevented from vibrating, because it is here brought 
in contact with the other ligament. 

Now there are small muscles which 
are attached to the arytenoid car¬ 
tilages for the purpose of moving 
them as I have pointed out. The 
figure which I have presented is a 
mere diagram, to show the arrange¬ 
ment of the ligaments for the pro¬ 
duction of the various notes of the 
voice. In Fig. 138 is represented 
the actual appearance of the liga¬ 
ments and the arytenoid cartilages, 
as you look down upon them. The 
ligaments you observe are thicker at 
their free edges than any where else. 

369. In Fig. 139 you have a view of the larynx and trachea 
rom behind, in which are shown two of the muscles that move 
he arytenoid cartilages. At h is the hyoid bone; t t , the 
posterior margins of the thyroid cartilage; between these 
stands the broad rear part of the cricoid cartilage, the 
middle line of which you see at c; at r are the rear ends 
of the rings of the trachea; l is the membranous part of the 
trachea, which lies in front of the oesophagus or gullet; a 
marks the top of one of the arytenoid cartilages, and you see 
also the top of the other; e is the epiglottis represented as 



FIG. 137. 
a 



Diagram showing the action of the 
VOCAL LIGAMENTS. 






_ THE VOICE. _ 

Muscles regulating the tension of the vocal ligaments. 


251 


FIG. 139 



REAR VIEW OF THE LARYNX AND THE TRACHEA. 

raised up as when we are speaking ; b is a muscle, which, be¬ 
ginning at the middle line of the cricoid cartilage, runs forward, 
and is fastened to the outside of the arytenoid cartilage, there 
being one like it on the other side, as you see; s is another 
muscle going from the cricoid to the arytenoid cartilage, which 
also has its fellow on the other side. You can see that the muscle, 
s, and its fellow, if contracted would bring the arytenoid cartilages 
nearer together, and so diminish the opening between the vocal 
membranes which are fastened to these pillars. The muscle, b , 
and its fellow, on the other hand, when they act, so draw upon 
the outer edges of the arytenoid cartilages as to separate these 
cartilages from each other, and therefore enlarge the openings 
between the ligaments. There are other muscles not seen in 
the figure, that alter the size of the orifice between the vocal 
ligaments and their degree of tension, and thus affect the notes 
of the voice. 

370. I have described the true vocal ligaments. But there 





252 


HUMAN PHYSTOLOGY. 


Interior view of the larynx and epiglottis. 


is another pair of ligaments directly above them, the space 
between which is the real opening into the larynx, upon which 
the epiglottis shuts down when we swallow. You will get a 
good idea of the arrangement of the two pairs of ligaments from 
Fig. 140. This is a representation of an inner view of one 


FIG. 140. 



INTERIOR OF THE LARYNX. 

half of the larynx, the division being made directly down, and 
from front to rear. At t is the front of the thyroid cartilage 
with its cut edge; at cc, are the two cut edges of the cricoid, 
showing how narrow is its front part compared with its broad 
rear portion ; a is the left arytenoid cartilage, c showing the 
place where it is united by a joint to the top of the cricoid; / is 
the trachea; r is the true vocal ligament or chord; v is the 
space between this and the upper ligament; and e is the epig¬ 
lottis which is shut down upon the upper ligaments as a cover 
by the contraction of the muscle 6, just when this is needed. 





THE VOICE. 


253 


Upper and lower ligaments. The lower the true vocal chords. 

In Fig. 141 is a diagram represent¬ 
ing the plan of these two pairs of 
ligaments, as shown by a perpendic¬ 
ular section from side to side. B B 
represents the vocal ligaments, C C 
the upper ligaments, and V V, the 
two recesses between them. 

3 71. We know that it is the 
lower ligaments that are the true 
vocal chords, because the parts 
above these, even the upper liga¬ 
ments, may be all cut away, and yet 
a vocal sound may be produced ; 
while if an opening be made into 
the larynx below the lower liga¬ 
ments the voice will be destroyed. 

Magendie, a French physiologist, 
speaks of a man, who on account of 
an opening in the larynx was never 
able to speak without pressing his 
cravat tightly against this opening, 
in order to prevent the air from escaping through it. Many 
experiments have been tried with the larynx after death to 
verify the results above stated. The lower ligaments are then 
the vocal chords, by the vibration of which all the different 
notes of the voice are produced. And the other parts of the 
vocal apparatus serve only to modify the sound caused by the 
ligaments. The lungs act merely as the “ wind-chest,” to hold 
the air which being forced out strikes on the ligaments, and 
makes them to vibrate. 

372. Let us now apply to this apparatus the principles 
which I have developed in the beginning of this chapter, as 
regulating the variation of note in common musical instru¬ 
ments. The size of the aperture, through which the sound i3 
thrown out, influences the note, of which we have a familiar 
example in whistling. And as you have seen that the size of 
the opening between the vocal ligaments is varied by the 
muscles moving the arytenoid cartilages, this must have an 
influence upon the note of the voice. But this is not the only 
cause of the variation of the note. As I showed in relation to 
the reed, and to the strings of stringed instruments, so also 
here the larger and less tense are the vibrating bodies, the vocal 
chords, the graver is the note, and vice versa. You have seen 

22 


FIG. 141. 








254 


HUMAN PHYSIOLOGY. 


Principles of musical instruments applied to the vocal apparatus. 

Iiow these chords or ligaments are varied in tension by the 
action of the muscles that move the arytenoid cartilages. You 
have also seen that, as these cartilages are brought near to¬ 
gether by the muscles, the extent of the free vibrating edges of 
the ligaments is shortened, because their edges are brought to¬ 
gether in their anterior part (Fig. 137). Magendie verified 
this by observation. He opened the throat of a noisy dog in 
such a way that he could look directly upon the vocal ligaments. 
When the sounds were grave, he observed that the ligaments 
vibrated in their whole length, and that the air passed out in the 
whole length of the chink between them. But when the 
sounds were on a high note, the ligaments did not vibrate in 
their anterior part, but only in the posterior, and the air passed 
out only at the open vibrating part. It is manifest that in pro¬ 
ducing the various notes, the muscles that move the arytenoid 
cartilages act upon the ligaments just as the lips do upon the 
reed of the hautboy or bassoon, regulating the extent and the 
rapidity of the vibrations. 

373. There has been much discussion as to the kind of 
musical instrument the larynx most resembles. From the facts 
above stated it appears clear that it most resembles reed instru¬ 
ments, though its analogy to stringed instruments is also quite 
apparent. There is also a resemblance to some small extent to 
common wind instruments, as the size of the orifice between the 
vocal ligaments must have some influence upon the note. 
Whatever we may think as to the degrees in which these 
analogies exist, we can see that the great principle of musical 
sounds is regarded in all the arrangements of the vocal appara¬ 
tus, viz., that coarse and slow vibrations produce grave notes, 
while rapid and fine vibrations produce high ones. 

374. I will trace the resemblance between the instrument of 
the voice and common musical instruments still farther. The 
sound as it comes from the larynx passes through a tube, just 
as the sound coming from a reed does in a reed instrument. 
In other words there is a body of inclosed air extending from 
the larynx to the outlets of the mouth and nose, which vibrates 
in transmitting the sound from the larynx. This body of air is 
not as simple in its form as that is which is inclosed in the tube 
of common reed instruments. It has three outlets, the mouth 
and the two nostrils. The sound of the voice, however, seldom 
comes out from the orifices of the nostrils, but almost always 
from the mouth. In humming it comes altogether from the 
nostrils. In ordinary speaking and singing the cavities of the 




THE VOICE. 


255 


Tube of the vocal apparatus like that of a reed instrument. 


nose act as reverberating cavities, the sound which reverberates 
there issuing from the mouth. This fact will be illustrated 
when I come to speak of the articulation of the voice. The 
curtain of the palate answers as a sort of swing door between 
the cavity of the mouth, and the cavities of the nose, to direct 
the air the one way or the other. When a sound is to be 
reverberated in the cavities of the nose, it hangs in such a way 
that the communication between the mouth and these cavities 
is open. 

375. You have seen that the tube connected with the reed 
in the reed instrument is so arranged, that the length of the 
confined column of air can be changed, in producing the 
different notes, the vibration of the air thus being brought into 
correspondence with that of the reed. How is the same thing 
effected in the vocal apparatus ? It is done in two ways. 
First, the length of the tube is altered. If you place your 
finger on the front of the larynx, and then sound various notes, 
you will feel the larynx rise when you sound a high note, and 
fall when you sound a grave one. The object of this move¬ 
ment is to alter the distance from the larynx to the outlet of the 
mouth, in other words, to alter the length of the column of air 
in the tube, so that it may correspond in its vibration with the 
vibration of the vocal chords. But the size of this column of 
air is altered in another way. It is altered in its width, which, 
as I have remarked in relation to musical instruments, § 362, is 
quite as effectual in changing the vibration as an alteration of 
length. The tube of the vocal instrument you readily see can 
be altered in its width by the muscles of the throat and 
mouth. 

376. The object of the tube of the reed instrument is, I have 
stated in § 366, to make the reed speak, as it is termed ; that is, 
to give intensity and an agreeable character to the sound. The 
tube in the instrument of the voice undoubtedly does the same 
thing. If the voice should come directly from the larynx with¬ 
out passing through the tube attached to it, it would be as dis¬ 
agreeable as the sound of a reed when separated from its tube. 
The voice gets most of its melody after it is made in the 
larynx, as it passes out through the column of air in the throat 
and mouth. And it is the variations of this tube produced by 
the muscles that surround it that give to the voice its variety 
of tone as well as its melody, thus constituting one of the 
great excellencies of the vocal instrument in comparison with 
all common musical instruments. If the voice of Jenny Lind 




256 


HUMAN PHYSIOLOGY. 


Seat of hoarseness. Influence of the epiglottis on the voice. 

could be made to come directly from the larynx, notwithstand¬ 
ing its great compass, it would lose all its charm, and would bo 
better fitted for the performances of Punch and Judy, than for 
the public concert. 

377. It is a very common popular notion, that a hoarseness, 
or a loss of voice, indicates disease in the lungs. But you have 
seen that the lungs are the mere bellows, or the “ wind-chest ” of 
the organ of the voice, and that the voice is produced by the vi¬ 
bration of the vocal ligaments as the air forced from the wind- 
chest strikes them, and is modified by the tube which extends 
from the larynx to the outlet of the mouth. Any alteration of 
the sound therefore, as hoarseness, must be caused by difficulty 
either in the ligaments, or the tube, or in both, and an en¬ 
tire loss of the voice can be caused only by an affection of the 
ligaments. Disease in the lungs, it is true, is very apt to affect 
the larynx and the throat by extension or by sympathy, and 
thus alter the voice ; but it often does not. Consumptive per¬ 
sons sometimes have a clear voice almost to the last. 

378. The epiglottis, besides acting as a lid for the larynx, for 
the food to pass over it into the oesophagus, also has an in¬ 
fluence upon the voice in two ways. First it can be made to 
narrow more or less the passage of air from the larynx. And 
secondly, some experiments of M. Grenie on reed instruments 
show, that it has an influence upon the intensity of the voice. 
When experimenting on some reed instrument, he wished to in¬ 
crease the intensity of sound without changing the reed. For 
this purpose he gradually increased the force of the current of 
the air; but this not only augmented the sound, but raised its 
note. He at length obviated the difficulty, by placing obliquely 
in the tube, just under the reed, a supple elastic tongue. He 
could now give greater intensity to the sound without raising 
its note. The epiglottis seems to perform the same office in 
our vocal tube, for it is elastic and supple like the little tongue 
which M. Grenie placed in the tube of his instrument. Its 
situation is similar also, it being directly over the double reed 
of the larynx, as we may call its ligaments. There are muscles 
to move it, so that it may be at the right inclination in all 
cases. One of these is seen in Fig. 140 at b. 

379. I have thus traced the analogy between the apparatus 
of the human voice, and musical instruments. How nicely ad¬ 
justed are all its parts ! With what precision must the muscles 
that move them act in those who are able to produce the most 
delicate, as well as the most striking variations of note ! Every 




THE VOICE. 


257 


4 


Delicacy of the action of the vocal muscles. Gliding from note to note. 

modulation of the voice, however slight, requires muscular ac¬ 
tion to effect it. The vocal ligaments must be put in just such 
a state, or the wrong sound will be produced. So too, the 
muscles of the mouth and throat must put the tube of the 
vocal instrument into the right shape, in order to have the con¬ 
tained column of air correspond in vibration with the vocal 
ligaments. To have some conception of the variety of the 
motions of the muscles concerned in the modulation of the 
voice, listen to some singer whose voice can command with ease 
and freedom a great extent of the scale. For every note that 
you hear there is a distinct and particular adjustment of the 
vocal ligaments, and of course a particular degree of contrac¬ 
tion of the little muscles that move them. Let us see how deli¬ 
cate the action of these parts is. It is calculated that the liga¬ 
ments vary in length only about the of an inch in producing 
all the notes of the voice. Now the natural compass of the 
voice (that is its range from its lowest to its highest note) in 
most singers is about two octaves or 24 semitones. Within 
each semitone a singer of ordinary capability can produce 5 or 
6 distinct notes; so that for the whole number of notes that he 
can sound distinctly 120 is a moderate estimate. He therefore 
produces 120 different states of tension in the vocal ligaments. 
And as the variation in their length for passing from the lowest 
of these 120 notes to the highest is only the £th of an inch, the 
variation required to pass from one note to another will be only 
the th of an inch. A very expert singer can produce a 
much more delicate action than this, and distinctly appreciate 
the result by his ear. How great the contrast between the 
minute contractions of the little muscles that move these vocal 
ligaments, and the contractions of the large muscles in the arm 
that wield the ax and the sledge-hammer! 

380. It is proper to notice here one very marked difference be¬ 
tween the vocal apparatus and common musical instruments. I 
have spoken in the previous paragraph of distinct notes as exe¬ 
cuted by the voice. Most instruments execute only these distinct 
notes. But the voice can also glide from one note to another 
with a continuous sound. In this respect the vocal instrument 
is superior to common musical instruments. There is one 
instrument, however, the violin, in which this gliding movement 
can be to a great extent imitated. It is done by sliding the 
finger on the string, as it vibrates under the bow. A peculiar 
use of this gliding movement distinguishes the voice of speech 
from that of song, as I shall show you in another part of this 

22 * 




258 


HUMAN PHYSIOLOGY. 


Training of the muscles of the voice. Importance of keeping the chest full of air. 

chapter. It is by an imitation of this, by sliding the finger on 
the string, that the violin can be made to imitate so well the 
tones of conversation. 

381. The muscles, by which all the variations in the tension of 
the vocal ligaments are effected, receive nerves from the brain, and 
are under the guidance of the will. When the mind therefore 
wills to produce a certain sound, these muscles immediately 
place the parts in such a state as to cause that sound. This is 
true of the muscles that put the tube in correspondence with 
the larynx, as well as of those which produce the right state of 
tension in the ligaments. It is also true of the muscles which 
articulate the voice, of which I am yet to speak, and of those 
which work the chest, the bellows or “wind-chest” of the organ 
of the voice. The muscles of this apparatus are in the same con¬ 
dition with other voluntary muscles; and therefore, like them, 
the more they are trained in the exercise of their powers, the 
more perfect will be their action. The muscles in the arm and 
hand of the infant learn to execute the motions of which they 
are capable gradually. Just '£6 it is with the muscles of the 
voice—from our infancy they are trained under the ear as an 
instructor. The muscles which regulate the adjustment of the 
vocal ligaments, in producing the different notes, cannot do it 
accurately without the education of exercise, any more than the 
lips of one just beginning to play on the hautboy or clarionet, 
can regulate their pressure on the reed, so as to sound the dif¬ 
ferent notes correctly. The analogy is perfect, for it is the 
muscles moving the vocal chords that vary the note of the voice, 
and it is the muscles moving the lips that vary their pressure 
on the reed, and of course vary the note of the instrument. 

382. The skillful singer or speaker exhibits much skill in 
managing the muscles of the “ wind-chest.” He keeps it all 
the time well supplied with air, so that but a comparatively 
slight action of the expiratory muscles will suffice to throw the 
air against the vocal ligaments with the requisite force. But 
an unskillful singer or speaker much of the time has his chest 
poorly supplied with air, and so speaks or sings, as it is expressed, 
from the top of the chest. It costs him, therefore, so much labor 
to throw out the air with sufficient force, that he is soon tired 
out. The necessity of keeping the chest full of air, in order to 
work the vocal apparatus easily, may be illustrated by reference 
to the bagpipe. If the bag containing the air be well filled, a 
slight pressure of the arm upon it will force the air through the 
pipe with sufficient rapidity to produce the sound. But if the 





THE VOICE. 

Tiring out the vocal muscles. Vocal apparatus in birds. 


259 


bag be flaccid, from the little quantity of air in it, a very strong 
pressure of the arm will be required to produce the same effect. 

383. But it is not the muscles of the chest only that are tired 
out in the unskillful singer or speaker, but also the muscles of 
the larynx and the throat. And a frequent tiring of these 
muscles weakens the force of the parts, and often at length 
produces disease. Much of the throat-disease of public speakers 
comes from this cause, and is a nervous disease, the affection of 
the lining membrane of the throat being often a mere accompa¬ 
niment. This result is more apt to occur when the nervous 
force of the system generally is impaired, than when there is a 
state of vigor. It is also more apt to occur in those who speak 
in a uniform and somewhat monotonous manner, than in those 
who have much variety in their mode of speaking. A continua¬ 
tion of precisely the same muscular effort for any length of time is 
apt to produce painful exhaustion, while a much greater amount 
of varied muscular effort may be put forth without weariness, 
or even with pleasure. 

384. It would be interesting to trace the differences in the 
arrangement of the vocal apparatus in different animals, but I 
will only notice the arrangement which we find in birds. The 
voice of birds is formed not, as in us, at the top of the wind¬ 
pipe, but at its lowest portion. Like the human voice, it is 
produced by the vibration of sheets of membrane. These are 
placed just at the division of the trachea, where its two branches 
go off to supply the two lungs with air. The voice is formed 
by these ligaments, and is then transmitted through the column 
of air contained in the whole length of the windpipe. This 
column of air must have some influence on the note of the voice, 
according to its length and diameter. Birds, therefore, in sing¬ 
ing different notes change its length in some measure. This is 
easily done, as the windpipe is composed of rings of cartilages, 
connected together by membranous substance. There are mus¬ 
cles indeed up and down the tube, for the purpose of shortening 

% it by approximating these rings to each other. As the turkey 
gobbles he throws his head up and down, and thus shortens 
and lengthens the trachea. This movement is quite obvious 
also in the canary bird. 

385. Having thus treated of the formation and the mod¬ 
ulation of the voice, I come now to its articulation, whxli 
makes it the grand medium of intercourse between man and 
man. I will first describe the parts engaged in articulation, and 
then speak of the agency of each of them. 






260 


HUMAN PHYSIOLOGY. 


Parts engaged in the articulation of the voice. 

386. The vocal tube, which I have described as extending. 
from the larynx to the outlets of the mouth and the nostrils, 
produces all the variety of pronunciation in all the different lan¬ 
guages of our globe. It is all one cavity, though it is partially 
divided by partition walls. If you recur to Fig. 10, on page 
48, you will see a representation of this compound cavity. At 
the top of the trachea d you see the epiglottis c, which shuts 
down upon its orifice when we are swallowing. Above this is 
a large space called the pharynx. It is the back part of the 
throat, which we can see behind the arch of the palate on 
looking at it through the open mouth. Its communication with 
the mouth and the cavities of the nose is regulated by the palate 
g, which is moved by muscles into the different positions required. 
The cavities are very complicated, having several partitions par¬ 
tially dividing them, as seen in Fig. 89, and they communicate 
with cells in the bones by small orifices. That very movable 
organ, the tongue, and the teeth and lips, I need not describe. 

387. We will now observe the agency which the different 
parts of this compound vocal tube have in the articulation of the 
voice. Every letter, whether it be a vowel or a consonant, re¬ 
quires a particular position of the different parts of the vocal tube. 

In some letters the tongue is the chief agent in articulation, in 
others the lips, in others the teeth, in others the palate, and there 
are some in the formation of which the cavities of the nose have 
an important agency. I will notice the different parts separately. 

388. The tongue has been considered so essential to speech, 
that tongue and language are often used synonymously. But 
though it does perform an important part in articulation, it is 
not absolutely essential. Though it assists in the formation of 
many of the alphabetical elements, it is the principal agent in 
but two of them, l and r. The loss then of this busy little 
organ does not necessarily produce dumbness, nor even impair 
to any great extent, in some cases at least, the power of speech. 

To prove this I will cite a few facts which appear to be well , 
authenticated. The Emperor Justin says that he had seen ven¬ 
erable men who, after their tongues had been cut off at the root, 
“complained bitterly of the torture they had suffered.” He 
says also in another place that some prisoners, who were pun¬ 
ished in this barbarous manner by Iionorichius, King of the 
Vandals, “ perfectly retained their speech.” But there are cases 
more thoroughly attested, having been examined and reported 
upon by scientific observers. A boy, who lost his tongue by 
disease at the age of eight years, was exhibited publicly because 




THE VOICE. 


261 


The tongue less essential than commonly supposed. Dentals. 

he could talk without a tongue. At the request of the members 
of the University of Saumur, the boy was brought before them 
by his friends. After a strict examination they were, perfectly 
satisfied as to the facts in the case, and recorded their official 
testimony to that effect. A very interesting account is given 
of another case in the Philosophical Transactions, in several 
papers published from time to time between the years 1742 
and 1747. It is the case of a girl who lost from disease the 
whole of her tongue, together with the uvula, (the little round 
body which hangs down from the middle of the arch of the 
palate,) and yet could talk and swallow as well as any one. 
So perfect was her articulation, that she could pronounce with 
exactness those letters which commonly require the agency of 
the tip of the tongue. She could sing finely, articulating with 
the same clearness as when she talked. The sockets of the teeth 
too were so much injured, that there were few teeth, and these 
rose so little above the gums, that they could not render much 
assistance, if any, in articulation. This case was investigated 
very thoroughly. The account was given to the Royal Society, 
attested by the minister of the parish, a physician of repute, 
and another respectable person. The Society, not wishing to 
give too easy a credence to so strange a case, requested another 
report from another set of witnesses appointed by themselves, 
and they gave them a series of questions to guide them in their 
investigations. The report which they made out coincided very 
minutely with the account first given. The case excited so 
much interest that the young woman was at length brought to 
London, and appeared before the Royal Society to satisfy them 
that she could really talk and sing, although she had no tongue. 

389. Some of the letters are formed principally by the teeth, 
as c, t , 5, z. They are therefore called Dentals. It is the too 
frequent and bungling employment of some of these which con* 
stitutes lisping. Those who have a tongue too large for the 
mouth are apt to lisp. In advanced age, when the teeth are 
lost, we find this defect of lisping. The reason is obvious. 
When the teeth are gone, the sockets gradually become oblit¬ 
erated, and that part of the jaw-bone where the teeth were, of 
course diminishes in size, making the mouth too small for the 
tongue. 

390. The letters, in the articulation of which the lips take 

the lead are v,w, &c, and are called labials. Chil¬ 

dren, when they first begin to talk, use labials freely, because 
they can see in others the motions necessary for their pronunci 




262 


HUMAN PHYSIOLOGY. 


Labials. Reverberation in some letters in the nasal cavities. 


ation, and then imitate them. Hence the endearing terms used 
by the child to the parent are, I believe, in all languages, or 
nearly all, composed of labials and vowels. And too, it is from 
the delight which the child takes in repeating over and over 
these terms, that we have the word papa and mama, ^instead 
of pa and ma. The same thing can be observed in other lan¬ 
guages as well as the English. If we teach a child to say 
father instead of papa, he finds little difficulty in articulating 
the first syllable, because it begins with a labial,/; but in the 
last syllable he will at first substitute for th the labial v, making 
it faver. Intoxicated persons, their lips being weak and trem¬ 
bling, are apt to make an awkward use of the labials, as well as 
of those letters in which the tongue has much agency. Per¬ 
sons with large lips also are apt to use the labials unskillfully. 
Sometimes one labial is used for another, as f for v , and p for 
b. This is very common among the Welsh. Shakspeare gives 
us an amusing case of this sort in Sir Hugh Evans in the Merry 
Wives of Windsor. “Ferry goot,” says he, “I will make a 
prief of it in my note book.” And so he says prains for brains, 
peings for beings, petter for better, <fec. The labial w is some¬ 
times used for v , thus, winegar, indiwisible, werry wigorous. 

391. The nasal cavities, it is obvious, must have a great 
influence in articulation. The letters m and n are partly nasal. 
In pronouncing m at the end of a syllable, as am, em, or om, 
we close the lips, and the sound issuing from the larynx rever- 
brates in the cavities of the nose. You can perceive this rever¬ 
beration by pressing gently upon the nostrils with the fingers 
while pronouncing this syllable. The same can be said of n, 
except that in pronouncing it we press the tip of the tongue 
against the roof of the mouth just behind the front teeth, pre¬ 
venting the passage of the air out through the mouth in this 
way, instead of doing it by closing the lips, as in articulating 
m. When m and n begin syllables, as in mo and no, the mouth 
is opened after the m or n is pronounced, in order to give utter¬ 
ance to the next letter. These are two distinct acts, but the 
one succeeds the other so quickly, that they appear to be a 
single act. The nasal sound ng is the one which we employ in 
humming. Hence, the mouth is kept closed and the sound issues 
from the orifices of the nostrils. 

392. A reverberation of sound in the back part of the mouth 
and the cavities of the nose constitutes a distinguishing peculi¬ 
arity of many of the consonants. Thus, in pronouncing b and 

the lips are placed precisely in the same manner, and the 




THE VOICE. 


263 


This reverberation in some consonants and not in others. 

only difference between them is that b has the reverberation 
spoken of, but p has not. If you pronounce these two letters 
in the syllables ap and ab, for example, while you press on the 
nostrils with your fingers, you can feel the vibration occasioned 
by this reverberation in pronouncing b, but there is obviously 
none in pronouncing^. This reverberation is heard in the follow¬ 
ing alphabetical elements, B, D, G, V, Z (the sound of s in the 
word as), Y, W, Th (as in thou), Zh (the sound of z in azure), 
Ng, L, M, N, R. Those which have not this reverberation are 
P, T, K, F, S (as heard in sun), H, Wh (as heard in which), 
Th (as heard in thing), Sh (the sound of s in sure). That you 
may contrast these two sets of alphabetical elements individually, 
I place them here in two rows. B is like P, except that it has 
a reverberation, and so on through. 

B, D, G, Y, Z, Y, W, Th, Zh, Ng, L, M, N, R. 

P, T, K, F, S, H, Wh, Th, Sh. 

393. In what is commonly called speaking through the nose 
the reverberation mentioned above 5 i§ disagreeably strong. The 
popular idea of it is incorrect, for this fault occurs in those who 
have some obstruction to the free passage of the air through 
the nose. This obstruction acts like the pressing of the nostrils 
with the fingers, confining more or less the body of air con¬ 
tained in the nasal passages. It is the vibration of this air thus 
partially confined in tortuous passages that produces the nasal 
twang. Any thing therefore which prevents the free outlet of the 
air from the nose will occasion it. Pressing the fingers on the 
nostrils while speaking, as already hinted, will produce it. A 
common example of it we have in what is called a cold in the 
head. The snuff-taker has this twang, because by such constant 
stimulation of the lining membrane it becomes thickened. 
Those who have this fault of “ speaking through the nose,” do 
not like others breathe ordinarily through the nose alone, but 
you see them sitting with their mouth constantly open, showing 
that there is so much obstruction in the nasal passages that 
they are not able to transmit sufficient air to the lungs. 

394. I have thus far spoken of articulation as employed in 
ordinary speech, that is with a vocal sound. But when no 
sound is produced by the ligaments of the larynx, as is the case 
in whispering, the noise produced by the passage of the air 
through the cavities of the vocal apparatus can be §o articulated, 
as to be heard distinctly at a considerable distance. Persons, 
therefore, who have entirely lost the voice can converse. In 




264 


HUMAN PHYSIOLOGY. 


Variation of note in whispering. Contrivances to imitate articulation. 

whispering the vocal ligaments are relaxed as they are when we 
simply breathe. But the sound of whispering has its high and 
low notes like the vocal sound. The variation of note is caused 
by variation of the size of the column of air contained in the 
vocal tube. This is effected chiefly by the tongue. In the high 
notes of whispering the tongue is nearer the roof of the mouth 
than in the low notes. The distinction between many of the 
letters as to reverberation noticed in § 392 holds in whispering 
as it does in ordinary vocal speech. 

395. You can observe the mechanism of the parts that is 
necessary for any one of the alphabetic elements, by pronoun¬ 
cing some syllable which it ends, prolonging the sound of the 
letter in question. And in doing this you will readily see the 
incorrectness of the common definition of consonants, viz., that 
they are letters which cannot be sounded without the aid of a 
vowel. Take, for instance, the lettter m in the syllable am. 
After getting an idea of the mechanism necessary for it by 
sounding it with a, you cajru*eadily sound it alone. It is proper 
to remark here, that in observing the distinctions between the 
alphabetical elements, you must bear in mind that the names 
which are given to the letters in the alphabet do not represent 
their sounds. For example, H (aitcli) and W (double-u) are 
nothing like the sound of these letters in have and wave. 

396. Various attempts have been made to imitate the artic¬ 
ulation of sounds by mechanism, but with very limited success. 
In 1779 a prize was offered by the Academy of Science at St. 
Petersburg, for the best dissertation on the theory of vowel 
sounds, and it was awarded to G. R. Kratzanstein, an account 
of whose experiments was published in the Transactions of the 
Academy. He found that the sound of the four vowels, A, E, 
O and U, might be produced by blowing through a reed into 
tubes, the forms of which are represented in Figures 142, 143, 
144 and 145, and that the sound of I, as pronounced by the 


FIG. 142 FIG. 143. FIG. 144. FIG. 145. FIG. 146. 

















THE VOICE. 


265 


Accurate adjustment of vocal and articulating muscles. 

French and other European nations can be produced by blowing 
into the tube, Fig. 146, by blowing at a without using the reed. 
M. Kempelen, of Vienna, the inventor of Maelzel’s automaton 
chess-player, carried the imitation of the human voice still 
farther. He produced an instrument capable of uttering certain 
words and short phrases in Latin and French. But it is not 
known exactly how he accomplished this, as he kept the matter 
secret. A gentleman of Cambridge, England, investigated this 
subject, and among other things found that by blowing through 
a reed into a conical cavity, the vowel sounds could be pro¬ 
duced by altering the size of the aperture for the passage of the 
air from the cavity, by means of a sliding board. I have alluded 
to these attempts to imitate the voice, to show by contrast 
the wonderful completeness and perfection of the vocal appa¬ 
ratus. Kempelen’s instrument, a box three feet long, could 
produce only a few words, but the instrument of the voice, 
although it occupies so little room in the body, can utter all 
words in all languages. 

397. We have now examined the whole of the vocal appa¬ 
ratus. You will observe that I have spoken of it as having two 
parts, the larynx, which is the reed of the instrument, and the 
vocal tube, which you have seen is quite complicated, for the 
purposes of articulation. Every action in both parts of the in¬ 
strument is produced by muscles. You have seen that the 
action of muscles is requisite to cause any, even the slightest, 
variation of note. So it is with the articulating apparatus, as 
it may be called. Every alphabetical element, (and in our lan¬ 
guage Rush makes 35 in the whole,) requires a particular ad¬ 
justment of the articulating apparatus. This adjustment is 
effected by muscles that move the tongue, lips, palate, &c. As 
these muscles then perform such varied movements, to produce 
this variety of note and articulation, it is no wonder that they 
require such long and diligent training. The child begins this 
long course of education the moment he utters an articulate 
sound. Observe him as he pronounces the syllable pa or ma y 
the first which children generally learn. He looks at his mother’s 
lips, and imitates the motion as well as he can. Cheered hy 
his success, and by her approving smile, he is constantly repeat¬ 
ing these first lessons in pronunciation to every one that $omes 
near him. Being as yet without skill in the use of these organs, 
he gives much more force than is necessary to the mechanical 
motions of articulation. For example, in pronouncing the word 
pa, he cl Dses his lips strongly, and not slightly as we do, and 





266 


HUMAN PHYSIOLOGY. 


Training of the muscles in speech. Skill in their use. 

when he opens it for the utterance of the word he does it with an 
explosive force, at the same time quickly bowing his head. The 
energy of his whole frame seems to be concentrated upon the 
effort. Day after day he strives to add to his stock of words, 
but his progress is slow; and as a sort of compensation for the 
leanness of his stock he repeats those which he has learned, and 
so of his own accord he says papa and mamma instead of using 
the words of a single syllable. In this education of the organs 
of the voice the ear is the principal instructor, but the eye, as 
you see, is also of great assistance. The little pupil, on hearing 
a sound which he wishes to utter himself, tries to imitate the 
motion which he sees is used in producing it, and he continues 
to try till his ear assures him that he has actually mastered 
the sound. Soon he is able to utter two different articulate 
sounds in succession; and he goes on learning year after year, 
till at length he can command all the sounds of his native 
tongue. And I may remark that it is in childhood and youth 
alone, that we can learn accurately and thoroughly the pronun¬ 
ciation of a language that is at all difficult in this respect. 
Hence a foreigner, however long he may live in a country, to 
which he goes in adult life, cannot wholly conceal his native 
accent. And we know how much such sounds as that of tli 
trouble the German and the Frenchman, unless they begin to 
learn the English language early in life. 

398. If we observe different persons while speaking or sing¬ 
ing, we shall see that some manage the vocal apparatus, or pla^ 
on the vocal instrument, as we may express it, with more skill 
than others. Listen to two persons in conversation, the one 
modulating and articulating his voice with a graceful melody, 
the other having an utterance harsh and awkward; and the 
contrast is as great as that between two instruments, one of 
which is well and the other badly played. In some you can al¬ 
most imagine that you hear the creaking of the machinery; while 
in others you do not once think of the mechanism of the voice, 
but your ear feasts upon its richly modulated and gracefully 
articulated sounds. It is as true of the muscles of the vocal 
apparatus as of those of any other part of the body, that skill in 
the management of them can be very much increased by exer¬ 
cise. The rope-dancer, by training his muscles, gives them a 
wonderful precision of action. The same thing can be done 
with the muscles that regulate the modulation and articulation 
of the voice. And in the most noted singers the little muscles 
which move the v ocal ligaments and those which adjust the 




THE VOICE. 


26 ? 


Stammering. The ear the instructor of the voice. 

parts of the vocal tube, must have a precision of action incom¬ 
parably more accurate and delicate than the large muscles in 
the limbs of the rope-dancer. If we compare the limited and 
bungling operations of the vocal apparatus in a little child just 
beginning to talk, with its infinitely varied but precise move¬ 
ments in a voluble speaker, or a skillful singer, we shall have 
some conception of the delicacy of motion, of which the muscles 
of this apparatus become capable by long continued exercise. 

399. There is a defective action of the muscles of the vocal 
apparatus, called stammering or stuttering, which I will just 
notice. It is an irregular spasmodic action of these muscles, very 
much like that which we see in the muscles of other parts of 
the body in the disease called St. Vitus’ dance. It is very much 
influenced by habit, and mental agitation aggravates it. Shak- 
speare gives the following accurate description of it. “I would 
thou wouldst stammer, that thou mightest pour out of thy mouth, 
as wine comes out of a narrow mouthed bottle, either too much 
at once, or none at all.” It is a singular and instructive fact, 
that many who stutter in ordinary conversation can read and 
sing as well as others. Dr. Good remarks that one of the worst 
stammerers he ever knew was one of the best readers of Paradise 
Lost that he ever heard. Such facts suggest some valuable 
principles in the treatment of this difficulty, which can be more 
easily overcome than is commonly supposed. 

400. Not only is the ear the educator of the muscles of the 
voice, but the dependence upon the ear is entire. The deaf and 
dumb therefore are in almost every case dumb because they 
are deaf. Their vocal organs are in a good condition, and the 
muscles are all there with their nervous connections. But the 
machinery does not work, for there is no guiding power to 
direct it. That this is the true view, is proved by those cases in 
which hearing has been restored, for such restoration is followed 
by that of the power of speech. Magendie relates an interest¬ 
ing case of this kind. It was the case of a young man deaf 
and dumb from birth, who had his hearing restored by M. Itard. 
He first heard the sound of the neighboring bells, which not 
only caused very lively emotions, but even headache and dizzi¬ 
ness. The next day he heard the sound of the small bell in 
the room, and shortly after he could hear the voice of persons 
speaking. His delight was then extreme, and he was so ab¬ 
sorbed in his 'new enjoyment that, says Professor Percy, “his 
eyes seemed to search the words even on our lips.” His voice 
was soon developed. The muscles of the vocal organs, so long 






268 


HUMAN PHYSIOLOGY. 


Absolute dependence of the voice upon the hearing. Seen in the deaf and dumb. 

inactive, began to wake up under the tuition of their instructor, 
the ear. Only vague sounds were formed at first, and, although 
after a while he could pronounce some words, he did it awk¬ 
wardly as children do when they are beginning to talk. He 
learned to talk very slowly. It would have been very interest¬ 
ing to have watched this case in its progress, but this was pre¬ 
vented by a disease which proved fatal. 

401. Few cases occur like that which is related above, but 
there are many cases in which the dependence of speech upon 
hearing is proved in another way. I refer to those cases in 
which the loss of the power of speech is obviously the conse¬ 
quence of the loss of the hearing. This is the case with children 
that become entirely deaf after they have made some progress 
in learning to talk. They cease to talk, and very soon forget 
the motions which they had learned to make in articulation. 
Sometimes some of these motions are remembered, and the 
individual can pronounce some words. But he does it very 
awkwardly, and the consciousness of this makes him very averse 
to trying it. A friend mentioned to me the case of a man who 
became deaf just after he had learned the alphabet. He re 
membered the mechanical effort necessary to produce each letter, 
but he had no control over the loudness or note of the voice, so 
that some of the letters he sounded very high, others low, some 
very loud, and others soft, making of course some laughable 
contrasts. It is undoubtedly possible to teach deaf and "dumb 
persons to talk to some extent, if we begin early enough ; but 
the power of speech, after the most persevering training, must 
be awkwardly mechanical, and exceedingly limited. Accord 
ingly all such efforts have been very soon given up. 

402. The question has probably arisen in your minds as to 
what the difference is between the voice of speech and the voice 
of song. The common notions on this subject were very indefi¬ 
nite until recently. But Dr. Rush, in his admirable work on the 
voice, has developed the true principles in regard to it. He 
has shown that we use the same notes in speech and song, and 
that the difference lies in the mode of using them. I will en¬ 
deavor to place before you the most prominent and material 
points in his view of this subject. 

403. If you pronounce the sound a as heard in day, you will 
observe that it ends in another sound, that of e. The Voice in 
pronouncing it rises through the interval of a tone, the sound 
at the same time gradually diminishing. So of other letters 
Thus, a as sounded in abends or vanishes in e as heard in err, o 




THE VOICE. 


26S 


Voice of speech anil of song. Explanation of emphasis. 

as heard in old vanishes in oo as heard in ooze; and ou as heard 
in our vanishes also in oo. The vanishing sounds are of course 
rather obscure and feeble. The first sound he calls the “ radical 
movement of the voice,” and the subsequent diminishing sound 
its “ vanishing movement/’ The rise of the voice during the van¬ 
ishing movement is not always through the interval of a tone, 
but it may be only a semitone, or it ''may be even through the 
interval of an octave. In singing the movement is very differ¬ 
ent. We pass “quickly and faintly through the radical move¬ 
ment to dwell with greater time and fullness on a note or level 
line of sound at the extreme place of the vanish.” Both in 
song and speech there is also a downward as well as an upward 
movement on the scale. The gliding of the voice on the scale, 
and its gradual vanish cannot be imitated on instruments. They 
may be imitated to some extent however on the violin if the 
finger moves along the string while the bow is drawn. The 
difference between the voice of speech and song is thus repre¬ 
sented by Dr. Rush: 



At 1 is represented the vanish on the interval of a tone; at 2 
on that of a third; at 3 on that of a fifth, and at 4 on that of 
an octave. 

404. I will notice very briefly the use of the vanishing move¬ 
ment in speech. In simple narrative the vanish never rises 
above the interval of a tone, as at 1. Whenever it rises higher 
it is either for emphasis or interrogation. The vanish on the 
interval of a fifth, as at 3, is the most common mode of interro¬ 
gation. That of the octave, 4, is used when the question is 
asked with great vehemence, or is accompanied with sneering, 
mirth, contempt, or raillery. Thus when the Jew in the Mer¬ 
chant of Venice asks, 

Hath a dog money? Is it possible 
A cur can lend ten thousand ducats ? 

there is a rise through the interval of an octave on the words 
cur and dog. You observe that the rise is on the words which 
are emphasized. Thus we can make four entirely different 

23* 

















270 


HUMAN PHYSIOLOGY. 


Use of the semitone in speech. Difference in capability of singing. 

sentences of the question, do you ride to town to day ? accord¬ 
ing as we make the rise on you, or ride, or town, or day. By 
the use of this rising vanish we can make a question of the 
most positive assertion, even of the blunt negative, no. 

405. The vanish on the interval of a semitone gives the voice 
a plaintive character, and it is therefore used for the expression 
of love, grief, supplication, &c. It is sometimes used so much 
as to give a general character of plaintiveness to one’s whole 
conversation. As a very clear and striking illustration of the 
power of the semitone we will take the cry of fire. Divide tb« 
word into two syllables, fi-yer, and ascend the scale thus: 



- - 0 -^——- 

| VL/ © 1 


— — -- 


Fi-yer. Fi-yer Fi-yer. Fi-yer. 


The two places of the semitones, indicated by the braces, will 
give the cry of fire as we commonly hear it. Sometimes we 
hear it cried in sport upon one note, and the sound is discordant 
and ludicrous. So also, the two words, “ 0 dear ,” sound like a 
mere mockery of grief, if uttered on one note, or any other 
interval than the semitone. 

406. Every one learns to talk, but there are many who do 
not learn to sing. Now as the same notes are used in the two 
cases, what is the reason of the difference? The reason is not 
in an absolute inability to appreciate the variations of note in 
sound, for these are practically appreciated in the use of the 
vanishing rise in conversation. There are two reasons for the 
difference. One is this. As the transitions of the voice from 
one part of the scale to another are much more varied in song 
than in speech, and are made by leaps instead of slides, song 
requires greater skill than speech does in the action of the mus¬ 
cles. Another reason is, that speech is a necessity, and song 
is not. We learn to speak therefore as a matter of course, but 
singing is a mere accomplishment. If it were learned as uni¬ 
versally as speaking is, there would be nearly as much good 
singing as good speaking. We can realize the truth of this 
assertion, when we observe the results of very early training in 
singing. And we should realize it still more if singing were 
universally considered, as it should be, as an essential part of 













THE EAR. 


271 


Ventriloquism. Difference between a sound ant u noise. 

the education of children. And I may remark in this connec¬ 
tion, that all have some measure of musical talent, though in 
some it is exceedingly small in amount. The difference in this 
respect in different persons is the same as the difference in re¬ 
gard to any other talent, as that of drawing for example. Skill 
is acquired in the same way in both cases, and its degree de¬ 
pends to the same extent, and in the same manner upon natural 
endowment. 

407. Some persons possess extraordinary powers in the use 
of the vocal organs. I refer to ventriloquism. This is a purely 
imitative art, and is not to be attributed to any peculiar forma¬ 
tion of the parts in the individual who possesses the power. 
The ventriloquist must have the faculty of appreciating with 
great accuracy the almost infinite variety of tones, articulations, 
and inflections of the voice, and must be able to imitate them 
with but little motion of those parts of the articulating apparatus 
which appear in view. lie at the same time makes skillful use 
of those circumstances, which will favor the false impressions 
in the minds of his audience, in relation to the locality of the 
source of the sounds. This is the simple explanation of this 
wonderful power. 


CHAPTER XV. 

THE EAR. 

In the last chapter I treated of the production of sound by 
the vocal apparatus. In this chapter I propose to show you 
how the impression of sound is transmitted to the brain, in 
order to produce the sensation of hearing. 

408. That you may the better understand the arrangement 
of the apparatus of hearing, I will first notice some of the 
principles that govern the transmission of sonorous vibrations. 
Sound may be produced by the vibration of any substance; 
though some are better fitted to produce it than others, and are 
therefore called sonorous bodies. When the vibrations which 
cause sound are equal, a musical sound results; but if they are 





272 


HUMAN PHYSIOLOGY. 


Reflection of sound. Speaking tube. Ear trumpet. 

unequal, we have a discordant sound, or what we ordinarily 
call a noise. Sound is transmitted from the point where it 
originates, in all directions. And its vibrations gradually les¬ 
sen, just as the ripples lessen which are produced by dropping 
a stone into the water. The vibrations of sound are reflected 
by objects against which they strike. For this reason the voice 
can be heard at a much greater distance if it be transmitted 
along a wall than when it is uttered in an open space. This 
may be illustrated on Fig. 147. Let A B represent a wall, and 

FIG. 147. 



C the position of the ear. If the bell at D be rung, besides 
the vibrations which come to the ear at C in the direct line 
C D, a vibration striking the wall at F will come to the ear in 
the line F C, and the same can be said of other points along 
the wall. An accumulation of vibrations, therefore, comes to 
the ear at C, which therefore receives a louder sound from the 
bell than it would if the bell were rung in a perfectly open 
space. For the same reason a speaker can be heard much more 
easily "within walls than he can be in the open air. The sound 
is reflected, and, therefore, in some measure concentrated by the 
walls. In speaking tubes this reflection and concentration are 
carried to a still greater extent. Sound can in this "way be 
heard at a great distance from its source. M. Biot found that 
when he spoke in*a whisper at one end of a tube, over three 
thousand feet in length, he was distinctly heard at the other 
end; so entirely do the walls of the tube prevent the diffusion 
of the vibration in the air around. Speaking tubes are there¬ 
fore used to a great extent in large manufactories, where direc¬ 
tions need to be given continually to workmen in different, parts 
of the establishment. The flexible tube, now so commonly 
made use of by deaf persons, furnishes another illustration. 
The vibrations of the voice received by the trumpet shaped end 
are transmitted through the tube to the ear. 








THE EAR. 


273 


Difference in the transmission of sound through solid, liquids, and gases. 


409. Sound may be transmitted through any substance, 
whether it be solid, liquid, or gaseous. It cannot be trans¬ 
mitted through a vacuum, for there is nothing there to vibrate. 
Sound differs in this respect from light, which passes as readily 
through a vacuum as it does through any transparent substance. 
The fact that sound cannot be transmitted through a vacuum 
is often illustrated by an experiment with the air-pump. If a 
bell be put under the receiver, and be set to ringing, as the air 
is exhausted by the pump, the sound becomes more and more 
faint, and at length it is not heard at all. For the same reason, 
a pistol fired on the summit of a mountain, gives nothing like 
so loud a report as when it is fired in the valley below. The 
more solid the medium is for the transmission of sound, the 
more readily is it transmitted. The scratching of a pin at the 
end of a long log may be heard by the ear applied to the other 
end, although it cannot be heard through the air, at even the 
distance of a few feet. Savages are in the habit of putting 
the ear to the ground to hear the step of their enemies when 
they apprehend their approach. A deaf gentleman, resting 
the bowl of his pipe on his daughter’s piano-forte as he smoked, 
found that he could hear the music with great distinctness; and 
many deaf persons can hear conversation, by holding a stick 
between their teeth, while the other end rests against the teeth 
of the person speaking. A knowledge of the ready transmis¬ 
sion of sound through solids suggested the examination of the 
chest in disease by the ear. If the ear be applied to the chest, 
the various sounds produced by the air, as it passes through 
the bronchial tubes into the air cells, can be heard through the 
solid walls of the chest, and thus the state of the lungs can be 
discovered. Water is a much better conductor of sonorous 
vibration than air, though it is not as good an one as a solid 
substance. The force of the vibration is lessened more gradu¬ 
ally in water than in air, and its rate of progress in water is, 
according to Chladni, 4,900 feet in a second, or between four 
and five times as great as in air. 

410. Sonorous vibration does not pass readily from one 
medium to another. Thus, although the scratch on the log is 
heard so easily by the ear at the other end, if the ear be 
removed a little from the log, it does not hear the sound, 
because the vibration is so much lessened in passing from the 
solid wood to the air. It is clear that the more unlike the two 
substances are, when sound passes from one to the other, the 
more will the vibration be lessened; for the more unlike they 




274 


HUMAN PHYSIOLOGY. 


Hearing a compound process. Only in part mechanical. 

are, the less easily will the one take the vibration from the 
other. For this reason, a sonorous vibration, produced in a 
solid body, may be transmitted to water with much less loss of 
intensity or force, than occurs when it is transmitted to air. 
And it may be remarked in this connection, that when vibra¬ 
tions are transmitted to a fluid, from air or from a solid, the 
intervention of a membrane is of essential service, for it pre¬ 
sents a firm surface upon which the vibrations can be received. 

411. The principles which I have thus noticed will be seen 
to apply to the arrangement of the apparatus of hearing, as 
we proceed in the examination of it. It has various parts for 
the different portions of the process which we call hearing. I 
will premise a mere general description of this process, before 
entering upon the examination of the apparatus in detail. The 
vibrations of sound, passing into the ear by a tube, strike at 
the bottom of that tube upon a drum. The air can go no far¬ 
ther, for this drum is perfectly air-tight. It communicates its 
vibrations, however, to the drum, which transmits them to a 
chain of four little bones, the last of which transmits them to 
another drum, covering an opening into various winding pas¬ 
sages in solid bone. In these passages is contained a limpid 
fluid, which is put in motion by the vibrations of the drum last 
mentioned. So much for the mere mechanical part of the pro¬ 
cess. In the winding passages are spread out the minute fibres 
of the nerve of hearing. The vibrations of the liquid in these 
halls of audience, as we may call them, make an impression 
upon these nerves, which is communicated to the brain through 
the trunk of the nerve, and this completes the whole process 
necessary to the production of the sensation of hearing. 

412. The parts of the apparatus of hearing may be seen in 
Fig. 148. The internal portions are made rather larger than 
natural, in order that the arrangement may be more clear. At 
a b c is the external ear; at d is the entrance to the tube of 
the ear/; g is the drum of the ear at the end of this tube, 
called the membrane of the tympanum; h is the cavity of the 
tympanum, the chain of bones which it contains being left out, 
so that the plan of the apparatus may be more clear to you; 
k is the Eustachian tube, which makes a communication be¬ 
tween the back of the throat and the cavity of the tympanum; 
n is a part of the winding passages, shaped like a snail’s shell, 
and is therefore called the cochlea; at m are three other wind¬ 
ing passages, called, from their form, semi-circular canals; and 
at l is the vestibule , or common hall of entrance to all these 




The parts of the apparatus of hearing described. 


FIG. 148. 



VERTICAL SECTION OF THE ORGAN OF HEARING 


winding passages. In the cavity of the tympanum, on the side 
opposite to the drum of the ear, you see two holes. These 
open into the winding passages, the larger one into their vesti¬ 
bule or entrance hall. Both of these holes are covered by a 
membrane, and to the membrane of the larger one is attached 
the last of the chain of bones. At o is the trunk of the nerve 
of hearing, and at e e is the bone that incloses these parts, 
which is so hard that it is called the petrous, or rock-like bone. 

Having given you this general view of the apparatus, I shall 
now speak of each part more particularly. 

413. The object of the external ear is to collect the waves of 
sound, and direct them into the tube of the ear. There have 
been many speculations in regard to the use of the prominences 
and ridges of the external ear, but they are fanciful and ground¬ 
less; and its surface is thus diversified, probably for the sake 
of making this organ a comely one. If the object were to give 
it the best shape and arrangement for collecting the vibrations 
of sound, it would have had a different shape altogether, and 











276 


HUMAN PHYSIOLOGY. 


External ear. Tube. Ear-wax. Drum and bones. 


would have been arranged with muscles which could turn it in 
different directions, as is the case with many animals. The 
shape of the external ear is much better in many animals than 
it is in man, if we consider its object to be merely the collec¬ 
tion of the waves of sound. The endowment is in this case, as 
well as in every other, according to the necessities of the case. 
The bat is guided so much in its movements by the sense of 
hearing, that it has of necessity very large ears, and they are 
so shaped as to collect, in the best possible manner, the vibra¬ 
tions of the air. With proportionably large, and similarly shaped 
ears, man could hear much better than he now does, but he has 
no need of such ugly appendages. In regard to the motions 
of the ears in animals, it is worthy of remark, that animals of 
prey can turn their ears forward with the most facility, while 
timorous animals turn their ears backward to keep warned of 
danger. 

414. The tube of the ear is about an inch long in the adult. 
It is formed of cartilage like the external ear, and ends at the 
drum. At its entrance are hairs which afford some protection 
against intruders. But the chief protection is the bitter wax, 
which is secreted by little glands, situated in the skin of the 
tube. The odor from this secretion so effectually keeps out the 
insects from this open entrance, that it is quite a rare occurrence 
to have an insect get into the ear. And when one does get in, 
the wax envelopes him, and commonly soon destroys him. 

415. The drum of the ear, which makes the closed end of 
the tube above described, as seen at < 7 , Fig. 148, is very thin 
and transparent. On the other side of it is the cavity of the 
tympanum h. In this cavity are the four bones. These are 
represented in Fig. 149, enlarged 
so that you can see their shape 
distinctly. They are named from 
their shapes. They are the mal¬ 
leus or hammer m; the incus 
or anvil i; the os orbiculare , or 
round bone 0 , the smallest bone 
in the body; and the stapes or 
stirrup-bone. The long handle 
of the hammer h is fastened to 
the middle of the drum of the ear. The little round bone is 
fixed between the slender end of the anvil, and the top of the 
stirrup-bone. In Fig. 150 you have a representation of these 
bonesj together with the drum of the ear. While the end of 


FIG. 149. 






THE EAR. 


277 


Eustachian tube. Winding passages of the internal ear. 



DRUM OF THE EAR 

with the bones. 


tlie handle of the hammer is fastened to FIG - 150 * 

the middle of the drum, the base of the 
stirrup is fastened to another drum, cover¬ 
ing the hole or window, opening into the 
vestibule of the winding passages. There 
are three very delicate muscles which move 
these bones. One of them relaxes the 
drum of the ear, and another makes it 
more tense; and thus the drum is put into 
the right states of tension, to accommodate 
it to the various kinds of vibration that come to it. This is a 
matter of some importance, for it is plain that while a relaxed 
drum can vibrate properly to grave sounds that enter the ear, 
it must be tense, in order to respond properly to the vibrations 
of the air in the higher notes. 

416. The cavity of the tympanum (h Fig. 148) in which the 
little bones are, and which is beyond the drum, communicates 
with the mouth by the Eustachian tube k. If you shut your 
mouth, and close the nostrils with the fingers, and then perform 
the action of blowing, you will feel the air enter the Eustachian 
tubes, and fill the cavity of the tympanum. The chief object 
of this communication is to have air on the inside as well as 
the outside of the drum, so that it may vibrate freely. The 
cavity of the tympanum might indeed have been a closed 
cavity, containing air. But it would then have been very much 
like a common drum, with the hole in its side closed. This 
would very much impair the vibration. 

417. We now come to another part of the apparatus of 
hearing—the winding passages. These are inclosed, as I have 
already stated, in the most solid bone in the body. They are 
called together, very appropriately, the labyrinth , sometimes 
the internal ear. This is really the essential part of the appara¬ 
tus. Here are the true halls of audience, where the nerve is 
posted, which receives the messages from without, and trans¬ 
mits them to the brain. The drum of the ear and the chain of 
little bones may be destroyed, and yet, if these winding pas¬ 
sages remain entire, with the membranes over the two windows 
that open into them, the hearing will not be lost; though it 
will be less perfect than it is when the whole of the apparatus 
is there, and in good order. Sir Astley Cooper relates the case 
of a gentleman, who lost the drums of both ears by disease. 
By shutting his mouth, he could blow the air out through his 
ears, with such force as to make a whistling noise, and to move 

24 





278 


HUMAN PHYSIOLOGY. 


Description of the winding passages. Their importance. 

the hair that hung from his temples. Yet he was not only able 
to hear with ease all common conversation, but he had a nice 
appreciation of musical sounds. Sir Astley says that “ he 
played well on the flute, and had frequently borne a part in a 
concert; and he sung with much taste, and perfectly in tune.” 

418. The labyrinth is represented much magnified in Fig. 
151. The middle part of it, v, is the vestibule. From this go 
out the semi-circular canals , 
x, y, z , on the upper side, and 
on the lower the winding pas¬ 
sages of the cochlea, k. At o 
you sec the opening called the 
fenestra ovalis , or oval win¬ 
dow. This is covered by a 
membrane, on which presses 
the base of the stirrup-bone. 

You see another opening r, 
which is called the fenestra 
rotunda , or round window. 

This is covered with a mem¬ 
brane. Both of these open¬ 
ings you see in Fig. 148, in 
the cavity of the tympanum, 
opposite to the drum of the 
ear. In these winding pas¬ 
sages is a watery fluid, the vibrations of which, acting upon 
the branches of the nerve distributed there, cause the sensation 
of hearing. Of course, if either of the membranes covering the 
openings into these passages be destroyed or broken, the fluid 
will run out from the ear, and there can be no more hearing, 
although the rest of the apparatus is perfect. The drum wili 
continue to vibrate as sounds strike upon it, the little chain of 
bones will repeat the vibration, but it will stop at the end of 
the chain, the stirrup-like bone. So too, although the mem¬ 
branes may be entire, and the whole apparatus may be perfect 
as a piece of mechanism, so that the succession of vibrations 
from the air without through the drum and the chain of bones, 
to the fluid of the labyrinth, is uninterrupted, if the nerve of 
hearing be paralyzed, so that it cannot be impressed with the 
vibration of the fluid that bathes its branches, there can be no 
hearing. Partial deafness is undoubtedly often owing to a 
thickening of the fluid in these passages, or to a partial failure 
of the nerve distributed in them. 





THE EAR. 


279 


Principles of transmission of sound observed in the arrangement. 

419. It will be proper to say a word here in relation to the 
choice of a fluid, instead of a solid or an aeriform substance, as 
the medium through which the impression of the vibration of 
sound is communicated to the nerve. It is better than a solid 
would be, so far as we can see, because no arrangement of a 
vibrating solid with the minute fibres of the branches of the 
nerve -could be effectual, and at the same time so little liable 
to derangement, as the arrangement of nervous fibres immersed 
in a liquid, and the whole inclosed in solid walls of bone. It 
is better than air would be, for at least two reasons. 1st. The 
vibrations of sound, as stated in § 409, are communicated with 
much more ease and rapidity through water than through air. 
This we see to be a consideration of some importance, when we 
look at the complicated and winding passages that contain the 
fluid. ‘2d. There is not as much loss in the force of the vibra¬ 
tion in the transmission from the solid stirrup-bone through the 
membrane to the fluid, as there would be if the transmission 
were to air. 

420. The whole arrangement in regard to material we can 
see to be admirable, if examined in relation to the known prin¬ 
ciples of the transmission of sound. We can see the object of 
the chain of bones. If these were left out of the arrangement 
we could hear, but not so well as we do now. For it has been 
ascertained by experiment, that the transmission is much more 
perfect when the vibration passes, as in the case of the ear, 
through a tense membrane, then through a chain of solid sub¬ 
stances, and from them through a second membrane to the 
fluid, than it is when the chain of solid bodies is omitted, and 
air is made to take their place. And when the vibration has 
arrived at the fluid in the' labyrinth, there is a contrivance there 
for increasing its intensity. There are two little chalky con¬ 
cretions suspended in this fluid by nervous fibres. These are 
found in all mammalia, and in fishes they are quite large and 
hard. This being the case, it was inferred that these bodies 
have some important influence upon the transmission; and it 
has been found by experiment that hard bodies thus situated 
in a fluid increase the sonorous vibrations in their neighborhood. 

421. You will remember that there are two openings into 
the labyrinth, from the cavity of the tympanum. Both are 
covered by membranes, one of which is pressed upon by the 
stirrup-bone, while the other is free. It was formerly supposed 
that the second opening was absolutely essential to the vibra¬ 
tion of the fluid in the labyrinth. For, as fluids are incom- 




280 


HUMAN PHYSIOLOGY. 


Mode of vibration of the fluid in the winding passages. 

pressible, it was inferred that, as the stirrup-hone communi¬ 
cated its vibration to the membrane of the fenestra ovalis , the 
fluid in the labyrinth would not vibrate, unless there was another 
opening some where, the membrane of which would yield to 
pressure. This, however, has been ascertained to be not strictly 
true. It has been proved by experiment that a sonorous vibra¬ 
tion can be transmitted through a confined fluid. Indeed there 
are some animals in which there is only one opening into the 
labyrinth. But, although this second opening is not essential to 
the vibration of the liquid, it undoubtedly makes that vibration 
more perfect. Although the second opening is so near the 
first, as seen in the cavity of the tympanum, (Fig. 148) yet in 
relation to the arrangement of the winding passages of the 
labyrinth, as you will soon see, it is really quite at the other 
end of it. The vibration then may be considered as communi¬ 
cated through a long tube, which has a membrane at both 
ends. And it is obvious that a vibration communicated to the 
membrane at one end, will more readily move the fluid through¬ 
out all the tube, from the yielding of the membrane at the 
other end. This will be more obvious, as I describe more par¬ 
ticularly the arrangement of the passages in the labyrinth, 
which I will now do. 

422. To recur to Fig. 151, the vestibule v, into which the 
fenestra ovalis o opens, is, as before stated, a sort of common 
entrance hall to all the passages of the labyrinth. I have 
spoken of the semi-circular canals x, y, and z , that lead out 
from this. These are simple canals. But the passages of the 
cochlea, Jc , are very complicated, and it is this fact that has 
given the name of labyrinth to the whole of the internal ear. 
The vestibule opens into the cochlea at its base. Now, the 
cochlea is so divided, that the passage into which the vestibule 
opens, runs around the pillar in the middle of it to its top, 
making just two turns and a half. It there opens into another 
passage, which makes two turns and a half back to the base of 
the cochlea. This passage does not end in the vestibule where 
the other began, but it ends in the round hole r, which opens 
into the cavity of the tympanum. This disposition of the 
parts of the cochlea may be seen in Fig. 152, which represents 
it as opened to show the arrangement of the walls of the two 
winding galleries. The pillar in the middle, around which 
these dividing walls are fastened, expands in the top into what 
is called a cupola, where the two spiral galleries communicate 
together. With this description, you can understand in what 





THE EAR. 


281 


Distribution of the nerve of hearing in the cochlea. 


FIG.152. 



THE COCHLEA OPENED. 


directions the vibration is transmitted, when it is received from 
the stirrup-bone, at the door of the labyrinth, by the membrane 
which covers it. It travels one way up the fluid in the three 
semi-circular canals. It travels another way through one spiral 
gallery in the cochlea to the cupola, and then down the other 
spiral gallery, reaching at length the membrane of the fenestra 
rotunda , or round window. 

423. I will now describe to you the arrangement of the 
branches of the nerve of hearing in these passages. The ar¬ 
rangement is different in the vestibule and the semi-circular 
canals from what it is in the cochlea. In all the cavities of the 
labyrinth, there is a thin, delicate lining of membrane, which 
secretes a watery fluid. In the vestibule and semi-circular 
canals, there is a second membrane. This is separate from the 
first membrane, and lies loose in the cavities. It makes a close 
sac, and as it extends from the vestibule into the semi-circular 
canals, it is very irregular in its form. This sac contains a fluid, 
and the fluid secreted from the membrane which lines the bone 
bathes the outside of the sac. Now, it is on the delicate mem¬ 
brane which forms this sac, that the fibres of the nerve are 
distributed, so that they may receive the impression of the 
vibration of the fluid. In Fig. 153, is a representation of this 
sac, with the distribution of the nerve. At 1, 2, and 3, you 
see the parts of this sac which line the semi-circular canals. 
At 4 is a junction of two of these canals, for what purpose we 
know not. At 6, 9, 10, and 11, are seen the terminations of 
branches of the nerve. At 8 and 13 are two of thase branches 

24 * 







282 


HUMAN PHYSIOLOGY. 


Distribution of the nerve in the semi-circular canals. 


FIG. 153. 



and at 14 is the branch of the nerve which goes to be distrib¬ 
uted in the cochlea. In Fig. 154 is represented one of the pans 

FIG. 154. 








THE EAR. 


283 


Beautiful arrangement of the nervous fibrils in the cochlea. 


where the nerve terminates, as at 10 in Fig. 153, much more 
highly magnified. You see the loop-like termination of the 
nervous fibrils. You can readily see that every vibration of 
the fluid would make an impression upon these nervous fibrils 
thus distributed upon this delicate membrane, which has the 
fluid upon both sides of it. 

424. The distribution of the nerve is after a different man¬ 
ner in the cochlea. Here there is no loose membrane, with the 
nerve distributed upon it, and the fluid each side of it, as in 
the vestibule and the semi-circular canals. But the nerve is 
distributed upon the division wall of the galleries in a very 
oeautiful manner. This is represented in Fig. 155, in which 2 

FIG. 155. 



is the nerve, and 3, 3, 3, show its distribution. These fibrils 
lie in little channels in a lamina,, or leaf of solid bone. But the 
bone extends only to 4, 4, and the remainder of the division 
wall is made of membrane, represented at 5, 5, 5. At 7 is the 
opening in the cupola, by which the two spiral galleries com¬ 
municate. At 1 you have these parts of the natural size. We 
know not exactly how this mechanism works, but the proba¬ 
bility is, that the nerve receives impressions from the vibrations 
of the fluid in two ways—directly from the fluid itself, and also 
from the vibration of the membrane to which the extremities 
of the nerve are attached, this membrane being shaken of 
course by the vibrating fluid. 

425. Having thus described the parts of the organ of hear¬ 
ing, I will trace for you, with some particuWity, the steps of 




284 


HUMAN PHYSIOLOGY. 


Steps of the process of hearing given in their order. 

the process of hearing, as it must occur in the case of every 
sound that produces that sensation. The vibrating air enters 
the tube of the ear, and, reaching the drum, produces a vibra¬ 
tion there. This vibration is communicated to the chain of 
bones, which, as Dr. Paley very aptly says, like a repeating 
line of frigates pass it on. It is transmitted from the last of 
this chain of bones, the stirrup-bone, to the membrane covering 
the fenestra ovalis , and from this to the fluid contained in all 
the passages of the labyrinth. The vibration goes through all 
the semi-circular canals in one direction, and in another up one 
gallery of the cochlea, and down the other. In all these cavi¬ 
ties, are spread out in various ways, the filaments of the nerve 
which receive the impression of the vibration. This impression 
is transmitted from the extremities of the nerve, through its 
trunk, to the brain, where the mind receives it. All this to¬ 
gether constitutes hearing; and all of it occurs in the case of 
any sound which we hear, however closely it may follow any 
other sound. 

426. Most of our hearing is done precisely in the way 
described, but not all. We sometimes hear directly through 
the bone surrounding the labyrinth. If you place a watch 
between the teeth, you hear the ticking; and it gives a very 
different sound from what it does when held to the ear, be¬ 
cause the sonorous vibration is transmitted directly through 
the solid bones of the skull from the teeth. In the same way 
was the sound transmitted in the case of the deaf old gentle¬ 
man, (§ 409) who heard his daughter’s music through tho 
stem of his pipe, as he rested the bowl of it on the piano. 
The fact thus illustrated is often made use of by physicians, in 
detecting the nature of the difficulty in cases of deafness. Thus, 
if a watch held between the teeth communicate a very distinct 
and loud sound to the ear, we infer that the internal ear is in a 
good condition, and that the difficulty is in some of the other 
parts connected with it, the drum, or the cavity of the tym¬ 
panum, or the Eustachian tube. 

427. I have described the apparatus of hearing as we find it 
in man. But it varies in different animals, according to the 
circumstances in which they are placed, and their necessities. 
Animals that live in water of course have a different appa¬ 
ratus of hearing from those that live in air. In most fishes tho 
semi-circular canals exist, but there is nothing like a cochlea. 
As sounds are transmitted so easily through water, (§ 410,) 
fishes have no need of so complicated and perfect an apparatus 




THE EAR. 


285 


Hearing in other animals. Only a part of the process of hearing understood. 


as animals that live in air. They are fitted to hear in their own 
element, and probably the moment that a fish is taken out of 
the water he becomes quite deaf, because his hearing apparatus 
is so poorly fitted to receive and transmit vibrations from the 
air. But in many animals that live in air the ear differs from 
that of man in its arrangements. The cochlea in birds is nearly 
straight instead of being spiral. Such facts lead to the infer¬ 
ence, that the peculiar arrangements in the hearing apparatus 
of man have regard, not merely to the medium in which he is 
placed, but to peculiar uses which are necessary in his case, as 
the determination of the direction of sound, the appreciation 
of its pitch and its character, the power of hearing very slight 
sounds, &c. The simplest form of apparatus found in animals, 
is a cavity excavated in bone, with a fluid shut in it by a mem¬ 
brane, and nervous filaments distributed so as to be impressed 
by the vibrations of the fluid. And this is all that is absolutely 
essential to hearing. 

428. Many speculations have been broached in regard to the 
special offices of particular parts of the labyrinth. Thus, it has 
been supposed that the semi-circular canals have an agency in 
informing us of the direction of sounds; for it is observed that 
they are always arranged in the same relative angle to each 
other. It has been supposed also, that the cochlea gives us the 
idea of the note of sounds, because it is noticed that the devel¬ 
opment of this part in different animals is in proportion to the 
variety of note which they produce. These suppositions, though 
quite probable, require farther investigation in comparative anat¬ 
omy to test their truth. 

429. In the process that makes up the sensation of hearing, 
there is one part which we can in some measure understand, 
and to which we can apply the known principles which govern 
the transmission of sonorous vibrations. But there is another 
part, that which links the process to the immaterial mind, that 
we cannot understand. We can trace the vibration received 
from the air through the several parts to the fluid in the laby¬ 
rinth, but here we come to a stand in our knowledge. The 
vibration stops here, and what is transmitted through the nerve 
to the mind we know not. We call it an impression; but this 
is only an indefinite word, implying simply that something is 
transmitted, without defining what it is. Neither do we know 
how the transmission is made. All that we do know is, that 
the nerve is essential to the completion of the sensation of hear¬ 
ing, and that it spreads out its minute fibrils or tubuli in the 




280 


HUMAN PHYSIOLOGY*. 


Ear equal to the eye in delicacy, beauty, and complication of structure. 

balls of audience, in order to receive impressions from the vi¬ 
brations that come there, and transmit them to the brain where 
the mind takes cognizance of them. Every part of the appa¬ 
ratus may be mechanically perfect, so that the vibrations 
may be transmitted to the fluid which bathes the nervous 
fibrils, but if the nerve be paralyzed, or if the communication 
between its extreme fibrils and the brain be in any way inter¬ 
rupted, the mind knows nothing of the vibration, and there is 
no hearing. 

430. The eye has generally been spoken of as being more 
wonderful than any other organ in the body, in view alike of 
the delicacy, the beauty, and the complication of its structure. 
But the apparatus of hearing presents a combination of these 
qualities quite as wonderful. There is nothing more delicate, 
and beautiful, and complicated than the arrangement of the 
nervous fibrils in the winding labyrinthic passages of the halls 
of audience. And as we trace the steps of the process of 
hearing, from the drum of the ear where the sound strikes, to 
the gray substance of the brain where the mind receives the 
impression, and think of each sound as sending a vibration 
through membranes and a chain of bones to the fluid in which 
the nervous fibrils are immersed, and of these fibrils as catching 
from every vibration of the fluid a definite impression and 
transmitting it to the mind, we see a mingling of the purely 
mechanical with the spiritual, which greatly enhances our ad¬ 
miration of the mechanism. Though the apparatus is compli¬ 
cated, the mechanical result is a simple one—it is a mere 
trembling of a fluid inclosed in winding cavities of bone. But 
simple as the result is, it is made, through the beautiful nervous 
connections of the ear with the brain, one of the chief inlets of 
knowledge to the mind, coming to it from nature’s multitudinous 
voices, and is a constant medium of communication for thought 
and feeling between man and man. Thus intimately in the 
human body are the simplest mechanical results connected with 
the complicated and diversified operations of the mind. In the 
process of hearing the drum of the ear is to be considered one 
end of the apparatus, and the gray portion of the brain the 
other. The drum simply vibrates; and instantaneously the 
mind receives a distinct impression from the vesicles of the gray 
matter. And thus is the communication established between 
the immaterial mind, and the vibrations of the material sub 
stances with which it is surrounded. 




THE EYE. 


287 


Seeing a compound process. Refraction of light. 


CHAPTER XVI. 

THE EYE. 

431. The sensation of sight is the result of a compound 
process, which may be divided into two distinct parts, as I re¬ 
marked in relation to the sensation of hearing, in § 429. The 
one part is purely mechanical, and the apparatus tor it is con¬ 
structed according to the common principles, which we find 
illustrated in optical instruments. The object of its arrange¬ 
ments is to form distinct images of objects in the back part of * 
the eye. The other part of the process is executed by the nerve 
of vision, called the optic nerve. This nerve, expanded upon 
the membrane where the images are formed, transmits impres¬ 
sions from these images to the brain, just as the nerve of hearing 
transmits to the brain the impressions which come from the 
vibration 6f the fluid of the labyrinth. 

Before proceeding to an examination of the eye as an optical 
instrument, I will call your attention to certain principles, which 
w'e shall find illustrated more beautifully and perfectly in the 
eye than in any optical instrument which man has ever con¬ 
structed. 

432. The rays of light coming from any luminous point go 
in straight lines in all directions, just as the vibrations of sound 
do, and, like them, become less intense the farther they are 
diffused. But they move in straight lines only so long as they 
remain in the same medium. When they pass from one me¬ 
dium into another they are bent out of their straight course, 
or refracted , as it is termed, unless they pass from one to the 
other in lines perpendicular to the 
surface of the medium which they 
enter. This may be illustrated by 
the following experiment. Place 
a coin, a, in the bottom of a basin, 
as represented in Fig. 156, and then 
withdraw from it so far that the 
coin may be hidden from your eye 
by the edge of the basin, as repre¬ 
sented in the figure. Keeping your 
eye fixed in that position, pour some 


FIG. 156. 















288 


HUMAN PHYSIOLOGY. 


Refraction as light passes from a rarer into a denser medium, and vice versa. 

water into the basin up to the level, c. The coin will again 
become visible to your eye. The reason is, that the rays of 
light, as they come from the water into the rarer medium, the 
air, are refracted or bent downwards, that is from the perpen¬ 
dicular. The effect of this may be seen in the figure. A ray 
of light, coming from the coin in the direction a, a?, does not 
pass to d , but is bent downward, and so passes to the eye at 
e. And so of other rays coming from the object. The coin, 
therefore, is seen by the eye at e , but it is not seen in its true 
direction from the eye which is in the line e, c, a. The only point 
in which the eye can see the coin in its true position is when 
the eye is at 6 , in a perpendicular line directly over it. A ray 
that passes from one medium to another in a line perpendicular 
to the surface of the medium into which it passes is not bent 
out of its course. All other rays are, and the more so the 
favther they are from the perpendicular. 

433. While rays that pass from a dense medium into a 
rarer, as from water into air, are bent from the perpendicular, 
those on the other hand, which pass from a rarer medium into 
a denser, as from air into water, are bent towards the perpendic¬ 
ular. Thus if in Fig. 156 a be the position of the eye of a 
fish, and where the eye is, at e, there be an insect, the fish can 
see it, because the ray that strikes the surface of the water, c, 
is refracted or bent towards the perpendicular line, 6 , a. And 
so of other rays. He does not see the insect, however, in its 
true direction, a, c, e, but it appears to him to be at d. For we 
always judge of the place of an object by the direction in 
which the rays from it strike the eye. 

434. When light passes from one medium into another which 
presents a convex or concave surface, instead of a flat one, a 
very great change is produced in the direction of its rays. 
Thus suppose, as represented in Fig. 157, three diverging rays 
coming from a point, a, through the air, enter a convex surface 
of glass, 6 , b'. The central ray a, c enters the glass in a direc¬ 
tion perpendicular to its surface, and therefore does not bend 
from its course. But the ray a, d enters very obliquely, and is 
bent towards the perpendicular at that point, e, and passes on 
in the direction /. So likewise the ray, a, < 7 , is bent towards 
the perpendicular h, and passes on in the line i. These rays 
diverging in the air have become converging in the glass, and 
the point at which they meet is called the focus. To this point 
all the other rays entering the convex glass converge also. 

435. But if the surface of the glass be concave , as represented 







THE EYE. 


2S9 


Refraction by convex and concave lense*. 


FIG. 157. 
O 



in Fig. 158. the diverging rays which enter it will he made to 
diverge still more. The ray, a , c , being perpendicular to the sur¬ 
face is unchanged in its course; but the ray, a, d , is bent towards 
the perpendicular, e, into the line /, and the ray, a, j t is bent to¬ 
wards the perpendicular h into the line i. In the case of both 


FIG. 158. 



the concave and the convex lens, the greater the curvature, the 
greater is the change of direction in the rays. The greater the 
curvature, therefore, the sooner are the rays brought to a focus 
in the case of the convex lens. 

There are other optical principles illustrated in the apparatus 
of vision, that will be brought out in the description of the 
eye, which I will now proceed to give. 

436. The arrangement of the different parts of the eye you 
can understand by Fig. 159, which is a mere map of a section 
of the eye, through its middle part from front to rear. It is 
intended merely to represent the arrangement of the parts dis¬ 
tinctly, without strict regard to proportion. The eye has three 

25 






290 


HUMAN PHYSIOLOGY. 


Description of the parts of the eye. 


FIG. 159. 



coats, as they are called. At a is the thick strong white coat, 
called the sclerotic coat, from a Greek word meaning hard. 
This, which is commonly called the white of the eye, gives to 
the eyeball its firmness. Into it the cornea , e, fits, like a watch- 
glass into its case. The sclerotic and cornea then make one coat 
of the eye, the outer one. Next comes the choroid coat, b. This 
is a very vascular coat, containing the minute branches of blood 
vessels which nourish other parts of the eye. It is of a dark 
color, for reasons which I will state in another place. Its color 
is owing to coloring matter contained in pigment cells, which 
lie along on the inner surface of this coat, next to the inner 
coat of the eye, the retina, c. The retina is a thin membrane, 
being principally composed of the expansion of the optic nerve, 
d. The eye has three humors, as they are termed. The first 
is the aqueous or watery humor,/, which is in a chamber be¬ 
tween the transparent cornea, e, and the crystalline humor, or 
lens, h. This chamber is divided into two parts by the iris, g, 
g , the pupil being the circular communicating door between 
them. The part of the chamber which is in front of the iris 
is much larger than that which is behind it. The crystalline 
humor, or lens , as it is more often called, has the consistency 
of half dissolved glue. At i is the vitreous humor, filling up 
a large part of the cavity of the eye. It is called vitreous from 
its* glassy appearance. It is a clear, jelly-like substance, having 
about the tenacity of white of egg. It is contained in an ex- 








THE EYE. 


291 


Arrangement of the front part of the eyeball. 

ceedingly thin and delicate sac, and this is divided into cells 
which contain the liquid. 

437. Fig. 160 is a map of the front part of the eye, in which 
the parts are more minutely delineated than in Fig 159. At 2 
is the sclerotic coat; 3, the cor¬ 
nea ; b, the crystalline lens ; a , a, 
a, the aqueous humor; 7, 7, the 
iris; 4, the choroid coat; 8, the 
retina; c, c, the vitreous humor, 
and 9, the sac containing it. 

Around the inside of the cham¬ 
ber containing the aqueous hu¬ 
mor is a very thin membrane, 

(represented as you see by a line,) 
which secretes the humor. In 
this membrane, as in the case of 
every other closed sac in the body, 
there are both exhalents and ab¬ 
sorbents, so that the fluid may be 
changed as necessity requires. 

There is another thin membrane 
of the eye which I have not yet 
described. It is represented by a 
line, 1, in the figure. It is the 
conjunctiva , so called because it 
unites or conjoins the ball of the 
eye with the eyelids. It covers 
the cornea, passes back a little way on the white of the eye, 
and then turns forward to line the eyelid. It is the seat of the 
most common form of inflammation in the eye. It is very vas¬ 
cular, as is shown by its distended vessels when it is inflamed. 
It is exceedingly sensitive, and hence the great pain which is 
occasioned by any thing, even the smallest mote, that gets into 
the eye. The object of having it so sensitive I have spoken 
of in the Chapter on the Nervous System, § 242. 

438. At 6 in Fig. 160, is one of the ciliary processes, as they 
are called, from their resemblance to the eyelashes. There is a 
circular row of them, numbering from sixty to eighty, so ar¬ 
ranged as to resemble the disk of a radiated flower. In Fig. 
161°they are represented as they appear in looking at them 
from behind, the back part of the eye being removed. At 1 
is the divided edge of the three coats; 2, the pupil; 3, the iris; 
4 , the ciliary processes. At 5 is the anterior edge of the retina, 


FIG. 160. 

4 ; 





292 


HUMAN PHYSIOLOGY. 


Object of the apparatus to form images of objects on the retina. 


FIG. 161. 


1 



CILIARY PROCESSES. 

which stops at the beginning of these processes, presenting, as 
you see, a scalloped appearance. The processes, however, do 
not arise from the retina, but come from the choroid coat, and 
are united at their origin by a ring of ligamentous substance 
to the sclerotic coat. The exact operation of this beautiful 
arrangement is not known, but it is pretty well ascertained, 
that muscular fibres are so connected with these processes, that 
when they contract they draw the crystalline lens forward. 
This, as you will see in another part of this chapter, is a very 
important movement in the adaptation of the eye to seeing at 
different distances. 

439. The object of all this apparatus, which I have de¬ 
scribed, is to have images of objects formed in the back part 
of the eye upon the retina, so that the optic nerve expanded 
there may carry impressions from them to the brain. This is 
done in this way. The rays of light coming from an object 
pass through first the cornea, then the aqueous humor, then 
the crystalline lens, and lastly the vitreous humor to the retina, 
where they, so to speak, daguerreotype the object. The fact 
that such an image is formed has been often proved by obser 
vation on the eyes of animals. If the eye of a rabbit be 
cleansed from the fat and muscles at its back part, and a candle, 
be held in front of it, you can see the image of the candle 
through the sclerotic coat, formed upon the retina. So if you 
take the eye of an ox, and carefully pare off the back part, so 







THE EYE. 

Images on the retina inverted. Camera Obscura. 


293 


as to leave it very thin, a distinct image of any thing placed in 
front of the eye may be seen at the back part. The image 
however will be inverted, as represented in Fig. 162. For the 


FIG. 162. 



sake of clearness two rays only are represented as coming from 
each of the two ends of the object, a, c. These rays cross each 
other in the middle of the eye, those from a being brought to 
a focus at 6, and those from c at d. As all the other rays, 
coming from other points in the object, are refracted in the 
same manner, a complete inverted picture of it is thus formed. 
The same thing is seen in the instrument called the camera ob¬ 
scura. If light be let into a darkened room through a small 
aperture in a window soutter, an inverted picture of objects 
without can be seen on a screen, as represented in Fig. 163. 

FIG. 163. 



This experiment, which can be performed by any one, illustrates 
in a rude way the principle of the camera obscura. The real 
instrument has a tube with a double convex lens, so as to collect 
together the rays from objects, and concentrate them upon a 
small space, thereby making a very distinct small image of 
them. The eye is a very beautiful and perfect instrument of 
this sort. The space filled by the vitreous humor is the dark¬ 
ened room; the pupil answers to the hole in the window shut- 

25* 












































































294 


HUMAN PHYSIOLOGY. 


Cornea. Iris. Its radiuted and circular muscular fibres. 


ter, or the tube of the more perfectly constructed camera; the 
crystalline humor is the lens; and the retina is the screen on 
which the images are formed. 

We will now attend to the agency which the different parte 
have in producing the result, for which the apparatus is con¬ 
structed, observing the perfect adaptation of each of them to 
the particular part which it performs in the process. 

440. The cornea, as it lets in the light, requires to be trans¬ 
parent, and, as it is very much exposed to injury, it “also re¬ 
quires to be very firm and hard. Both of these objects are 
secured in an admirable manner. Its transparency is secured 
in this way. It is made of different layers, which are kept 
moist by a delicate transparent fluid. It is this which in health 
makes the eye so clear and sparkling. Disease often so lessens 
it, as to give this window of the eye a dull appearance. The 
cornea is, as you see by Fig. 159, more convex than the sclerotic 
coat, so that it may act with some power as a lens in making 
the rays converge. 

441. The iris is a circular curtain with a round opening in 
its centre, the pupil, which can be varied in size to a consider¬ 
able degree. On the iris depends what is called the color of 
the eye, which is various, as blue, nearly black, grey, hazel, &c. 
The color is owing to the pigment which is in cells on its inner 
surface. The chief office of the iris is to regulate the quantity 
of light that enters the eye. When the light is obscure the 
opening in the iris is widely dilated; but when there is much 
light it is contracted; and if the light be excessive, it is con¬ 
tracted almost to a point.. Its motions, therefore, considering 
ing its small extent, have a very wide range. You can realize 
this if you look at the eye of some one in a dim light, and then 
suddenly bring a lighted candle very near to it. These motions 
are effected by a peculiar arrangement of muscular fibres, of 
which the iris is in part composed. There are 
two sets of fibres, the circular and radiated, as 
represented in Fig. 164. When the circular 
fibres contract, the pupil is contracted; and when, 
on the other hand, the radiated fibres contract, 
the pupil is dilated. There must be a very nice 
adjustment of the fibres, to enable them to di¬ 
late the pupil as widely as they sometimes do, 
without producing any puckering of the surface of 
the iris. The opening in the iris is always round in man ; but 
.n animals whose range of vision requires to extend widely in 


FIG. 1G4. 





THE EYE. 


295 


Crystalline lens. Seat of cataract. Choroid coat. Why dark. 


FIG. 1G5. 


Crystalline Lens. 


FIG. 16G. 


a horizontal direction, (as the herbivorous animals,) it is in the 
form of an ellipse, with the long diameter horizontal. In ani¬ 
mals, on the other hand, that leap up and down in pursuit of 
their food, as the cat and other carnivorous animals that seek 
their prey in the same manner, the pupil has the elliptical 
form, but with the long diameter vertical. 

442. The crystalline lens is the chief agent in the eye in con¬ 
centrating the rays of light by refraction. In Fig. 

165 you have a side view of it. Its anterior part, 

1, is less convex than its posterior, 2. In Fig. 166 
is a magnified view of the lens hardened in spirit 
and cut open, so as to show the different layers of 
which it is formed. The layers are more and more 
hard as you go towards the centre. The object of 
this arrangement aud of the peculiar shape of the 
lens, is not as yet understood. 

This lens is the seat of the disease 
called cataract. In this disease 
the lens becomes opake so as to 
prevent the rays of light from pass¬ 
ing to the retina. There are three 
ways of getting rid of the difficulty. 

One is to introduce an instrument 
shaped like a needle into the side 
of the eyeball, with which the opake 
lens is pushed off one side in the 
vitreous humor, so as to be out of 
the way of the rays of light. An¬ 
other is to break up the lens with the needle, so that its frag¬ 
ments may be absorbed. The third method is to make an 
opening in the cornea, and to extract the lens through it. 

443. The choroid coat ( b , Fig. 159) contains quite a large 
share of the minute bloodvessels, and nerves of the eye, and 
serves for a medium by which they pass to other parts of this 
organ. But it serves another important purpose by means of 
its dark pigment. It makes a dark chamber of the back part 
of the eye where the optic nerve is expanded. The object of 
this is to secure distinctness in the images formed upon the 
retina. If the choroid coat were of a light color, there would be 
so much reflection of the rays of light back and forth in all 
directions in the eye, that the pictures formed upon the retina 
would be confused. There would be a glare of light, such as 
we experience in a room where the walls are all of a very light 







296 


HUMAN PHYSIOLOGY. 


Want of pigment in the choroid of the albino. The retina. 

color. There is the same reason for having the chamber of 
the eye of a dark color, as for having that of the camera ob- 
scura so. In the albino there is a deficiency of the pigment of 
the choroid; and, therefore, in a bright light there is in his case 
a defect of vision, from the cross reflection to which I have 
alluded. During the day his vision is very indistinct; and it is 
only when twilight appears that he can see well, or with com¬ 
fort. The pigment is also deficient in the iris of the albino; 
and the bright red or pinky hue of the iris in his case is owing 
to the blood in the minute bloodvessels, with which this part 
is so well supplied. Those animals that use their eyes mostl) 
in daylight have the pigment of the choroid of the darkest 
color; while, on the other hand, those that need to see most 
clearly at night, as the owl, either have none of this pigment, 
or have it of a very light color. 

444. The retina is a soft greyish delicate membrane, formed 
chiefly of the expansion of the optic nerve. Here the images 
are formed, and the minute fibres of nerve in this membrane 
receive impressions from these images, which are transmitted to 
the brain by the trunk of the nerve. This nerve has the same 
relation to light that the nerve of hearing has to sound, the 
nerve of smell to odors, or the nerve of touch to the qualities 
of bodies that we feel. And it is curious to observe that the 
termination of the nerve of sight on the surface of the retina 
is arranged in papilla , just as the terminations of the nerves 
of touch are. In Fig. 167 is represented 

a portion of the retina of a frog magni- fig. 167. 

fied three hundred times. The upper 
rows of papillae, which are without dots, 
are seen sideways. 

445. The superiority of the eye, as an 
optical instrument, is seen in a striking 
manner in several particulars, in which 
difficulties and defects to which all opti¬ 
cal instruments are liable are removed. There is, for example, 
a defect in the operation of lenses in optical instruments, which 
is termed spherical aberration. This can be explained on Fig. 
168, which represents a lens, L, I/, with some of the rays as 
they pass through it. Now the rays R, R", R'", are brought 
to a focus at F; while the rays R, L and R"", 1/ come to a 
focus much nearer, at l. It was found by experiment, that if the 
central portion of the lens be covered, so that the rays R', R" 
R"', cannot pass, a distinct image will be formed on a screen 






THE EYE. 


297 


Spherical and chromatic aberration. How remedied in the eye. 
FIG. 168. 



put at Z. And, on the other hand, if the outer portion of the 
lens he covered, so that the outerrays are intercepted, then the 
middle rays, R/ R 7/ R'" will form an image on a screen at F. 
But if the whole lens be used, no distinct image is formed, wher¬ 
ever you may place the screen. If you place it at Z, it will 
receive with the rays that come to a focus there, rays that have 
their focus at F. And so of other points. 

446. It is in view of such experiments, that a contrivance 
has been adopted in the construction of telescopes and micro¬ 
scopes, for the purpose of remedying the difficulty above de¬ 
scribed. What is called a diaphragm , or stop , is put in against 
every lens. It is a perforated partition which permits the light 
to pass only through the central portion of the lens. The lines 
D, D', in Fig. 168, cutting off all rays in the neighborhood of 
R and R"", show the operation of the stop. In the eye the 
iris acts as the diaphragm or stop to the crystalline lens which 
is behind it, as you can see by recurring to Fig. 159. Ordina¬ 
rily, by means of this stop, the rays pass through only the 
central part of the lens. 

447. Another difficulty attending the operation of a common 
lens is what is termed chromatic aberration. Every ray of white 
light consists of a mixture of rays of seven different colors. 
Some of these colors are more easily refracted than others, and 
therefore on passing through a lens will come to a focus sooner. 
This of course is apt to make some confusion in the color and 
the distinctness of objects, when seen through a single lens, or 
through several if they are alike. The difficulty has been rem¬ 
edied, although Sir Isaac Newton thought that it never would 
be. And it is said that the hint of the remedy was taken from 
the arrangement of the eye. At any rate, the defect is avoided 
















298 


HUMAN PHYSIOLOGY. 


Adjustment of the eye to objects at different distances. 

by having lenses made of different materials, just as is the case 
in the eye. Thus if two lenses be used, one of which is made 
of flint and the other of common glass, the difficulty disappears. 
In the eye it is perfectly avoided by the passage of the rays 
through so many different materials, before it reaches the retina. 
The stop has been found a partial remedy in the case of optical 
instillments; and the iris, the stop of the eye, of course acts in 
, the same way. But the full remedy was not found, till another 
step was taken in imitation of the eye, the most perfect of all 
optical instruments. 

448. There is another arrangement in the eye, which the 
optician can imitate only in a comparatively bungling manner. 
It is that by which the eye adapts itself to different distances in 
looking at objects. If we look through a telescope at a near 
object, and then turn it towards one at a distance, we cannot 
see it distinctly until we adjust the lenses to suit the distance. 
But in the eye how quickly the adjustment is made! It is 
done ordinarily, without any effort on our part of which we are 
conscious. It is done so easily that we do not think of the 
change. We look at an object at a few inches distance, and in 
an instant turn the eye and see an object afar off with almost 
equal distinctness. There has been much discussion in regard 
to the means by which this adjustment is effected. One of the 
means undoubtedly is, a change in the relative position of the 
crystalline lens, which is effected by the muscular fibres spoken 
of in § 438. These fibres when they contract, draw the lens to¬ 
wards the front of the eye, and away from the retina. This is 
done whenever we look at a near object. If it were not, the rays 
which come from the object, as they diverge considerably, would 
not be brought to a focus when they reach the retina. The 
iris also has some agency in adjusting the eye for seeing at 
different distances. When the eye is turned to a near object 
the pupil always contracts, thereby shutting out those rays 
coming from it which are the most divergent. 


FIG. 169. 










THE EYE. 


299 


Difficulty in the near-sighted and the far-sighted. 


449. In some cases this power of adjustment is counteracted 
by defect in the arrangement of the eye. Thus, in the near - 
sighted , either the cornea or the crystalline lens, or both, are 
too convex; or, the crystalline lens is too far from the retina. 
The result is, that the rays of light coming from a distant ob¬ 
ject come to a focus before they reach the retina, as represented 
in Fig. 169. All objects, therefore, are seen indistinctly except 
those which are brought near to the eye. This defect is rem¬ 
edied by the use of a concave lens, which counteracts the effect 
of the too highly refractive power of the eye by making the 
rays divergent, instead of parallel, before entering the eye. By 
an habitual adjustment of the eye for seeing near objects, near¬ 
sightedness may be produced. Hence it is that engravers, 
watch-makers, students, &c., are so liable to become near sighted. 

450. In the far sighted the difficulty is of an opposite char¬ 
acter. The refractive power of the eye is too feeble. This is 
owing either to too little convexity of the cornea, or of the 
crystalline lens, or of both; or, to too great nearness of the 
crystalline lens to the retina. In this case the rays coming 
from a near object do not come to a focus soon enough. The 
focus of the rays coming from any point of the object is behind 
the retina, as seen in Fig. 170, in which the rays from two 


fig. no. 



points are represented as prolonged till they meet at their focus 
behind the retina. This defect is palliated by the use of convex 
glasses. It is quite common in persons who have passed middle 
age ; while near-sightedness appears mostly in younger persons, 
the full compliment of the humors of the eye in their case 
making the front part of the organ prominent. 

451. There has been much discussion of the question why 
we see every thing in its real position, while the images of ob¬ 
jects are, as you have seen in § 439, reversed on the retina. It 
has been supposed by some that we really see every thing re¬ 
versed, and that our experience with the sense of touch, in 
connection with that of vision, sets us right in this particular. 








300 


HUMAN PHYSIOLOGY. 


Y, r.f we see things erect, though their images on the retina are reversed. 

And this, it is supposed, is the more readily done from the fact, 
that our own limbs and bodies are reversed as pictured on the 
retina, as well as objects that are around us, so that every thing 
is relatively right in position. But if this be the true explana¬ 
tion, those who have their sight restored, after having been 
blind from birth, should at first see every thing wrong side up, 
and should be conscious of rectifying the error by looking at 
their own limbs and bodies. But this is not so. In the case 
related by the anatomist Cheselden, of the boy who was blind 
from birth, and who at about the age of thirteen had his sight 
restored by an operation, there was no complaint that he did not 
see things erect at the first. If this difficulty had existed, he would 
have complained of it quite as readily as he did of the difficulty 
in estimating the size and the distance of objects. The above 
explanation of erect vision, and other explanations of a similar 
character, are based upon a wrong idea of the office which the 
nerve performs in the process of vision. It is not the image 
formed upon the retina which is transmitted to the brain, but 
an impression produced by that image. The mind does not 
look in upon the eye and see the image, but it receives an im¬ 
pression from it through the nerve; and this impression is so 
managed that the mind gets the right idea of the relative position 
of objects. Of the way in which this is done we know as little 
as we know of the nature of the impression itself. 

452. It is an interesting and wonderful fact, that as we look 
at an object with both eyes, although there are two images 
formed, and therefore two impressions are carried to the brain 
by the two nerves, yet a single impression is produced in the 

FIG. 171. 








THE EYE. 


301 


Correspondence of action between the two eyes. 

mind. To produce this single effect at the end of the process 
of seeing, it is manifest that there must be a very exact corres¬ 
pondence in the two eyes as optical instruments. The two 
images must be similar, and must be formed on corresponding 
parts of the retina in both eyes. Thus, if there be a range of 
objects, as at A, B, C, in Fig. 171, the impression will be a 
single one in the mind, because the picture of these objects is 
on the same part of the retina in both eyes, a, b , c, and a', b ', c'. 
But if you press with your finger one of the eyes a little out 
of its place, all these objects will appear double, because their 
images occupy different parts of the retina in the two eyes. 

453. It is essential, therefore, that the muscles which move 
the eyes, as we direct them towards different objects, should 
harmonize in their action. They must move together with 
great exactness, or there will be disarrangement of vision. If the 
want of correspondence be slight, the vision will be merely 
confused. But if it be considerable, so that the images are 
formed on quite different parts of the retina, in the two eyes, 
every object will be distinctly double. You can verify this, by 
pressing one of your eyes with the finger with different degrees 
of force, while you look at the objects. The intoxicated man 
often sees indistinctly, and sometimes even double, from this 
want of correspondence in the action of the muscles moving 
the eyes. This is one of the causes of double vision, as we see 
it occurring in disease. I will cite a case which has recently 
come under my care, in illustration. The patient could see as 
usual, so long as he looked directly in front, or towards the 
left. But when he turned his eyes to look towards the right, 
he saw every thing double, and the farther he looked in that 
direction, the farther apart were the two images of every ob¬ 
ject. The reason was obvious. In looking to the right, the 
left eye turns towards the nose, while the right eye turns from 
it outward. The failure in this case was in the action of the 
muscle that turns the right eye from the nose. The conse¬ 
quence was, that as he attempted to turn his eyes to look to 
the right, the right eye did not correspond in its motion with 
the left, but remained nearly stationary, presenting therefore a 
squinting appearance. In common squinting, there is a per¬ 
manent contraction of one of these straight muscles, similar to 
that which we see in wry-neck, as stated in § 308. When 
this difficulty exists, the images of objects are formed in two 
different parts of the retina in the two eyes, as in the case which 
I have just related. We should therefore expect that there 

26 




302 


HUMAN PHYSIOLOGY. 


The two images of an object in the two eyes not always exactly alike. 

would be double vision, but ordinarily there is not. Why is 
this? It is because the mind acquires the habit of attending 
to the impression that comes from one eye alone, the sound on . 
If the squinting occur suddenly there is double vision at firs 
because it takes a little time for the mind to acquire tfie hab* 
referred to. But it generally comes on gradually, and there¬ 
fore there is no difficulty in the acquisition of this habit, to 
meet the exigency of the case. 

454. While it is necessary to single vision when both eyes 
are used, that the image of the object should occupy corres¬ 
ponding portions of the retina in the two eyes, it is not true 
that these two images are in all cases exactly alike. They are 
so when the object presents a plane surface, or one, every line 
of which can be seen equally well by both eyes. But if the 
object be such that some lines or surfaces of it are seen by one 
eye alone, while other lines and surfaces of it are seen only by 
the other eye, two different images are obviously formed in the 
two eyes. You can verify this by a simple experiment. If 
you hold a book before your eyes, with its back in a vertical 
direction, you see the back of the book and its sides at once, as 
a single object. If now, still holding the book in the same 
position, you shut one eye, you see but one side of the cover of 
the book—that one which is on the same side with the open 
eye. And so with the other eye. The plain inference is, that 
when you look at the book with both eyes, the image formed 
in the right eye is composed of the back of the book and the 
cover of the right side, while the image in the left eye is com¬ 
posed of the back of the book and the cover of the left side. 
From these two distinct images, of course, two distinct impres¬ 
sions are sent to the brain; and yet but a single impression is 
recognized there by the mind, for the book is seen as a single 
object. This single impression must, therefore, result in some 
way from a mingling of the two impressions transmitted along 
the two optic nerves. Were it not for this mingling of the two 
impressions, we should see double, that is, see two things, when¬ 
ever we look at any solid projecting object, and should see 
single only when we look at plane surfaces. Indeed, one who 
has but one eye can not acquire from sight alone any idea of 
solidity. Every thing would appear to him to be on a plane 
surface, till he finds it to be otherwise by the use of the sense 
of touch, in connection with that of sight. 

455. The statements in the last paragraph are beautifully 
illustrated by the instrument contrived by Professor Wheatstone, 






THE EYE. 


303 


Explanation of the stereoscope. 


which he calls the stereoscope. In using this instrument, you 
look at two pictures of the same object with the two eyes, and 
yet you see but one thing—that is, but one impression is pro¬ 
duced in the mind, although two different pictures are made in 
the two eyes, and of course two different impressions are con¬ 
veyed to the brain. Suppose the object represented is a book, 
as described in the experiment alluded to, in § 454. In the 
right half of the instrument is a representation of the book, as 
seen by the right eye, and in the left half is a representation of 
it as seen by the left eye. As you look at them you see but 
one book, just as you do in holding the book before your eyes. 
The two different images formed in the two eyes are the same 
in the two experiments. The same thing is done with other 
objects. Thus, the two representations of a dog, seen in Fig. 
172, are seen in the instrument as a single dog. You observe 

FIG. 172. 



that they are shaded differently. They are representations of 
the two pictures, which a dog in this position would make on 
the retina in both of the eyes of a person looking at him. 
When you look at them in the instrument, the single dog that 
you see stands out more than either of the two representations, 
as seen when they are not in the instrument. The reason is 
obvious. In the two images formed in the eyes, as you look 
into the instrument, are all the lines of light and shade, which 










304 


HUMAN PHYSIOLOGY. 


Rude imitation of the stereoscope. 

you would see in looking at a real dog with both eyes; while 
either one of these representations contains only a part of these 
'ines. You can imitate in some good degree the effect of the 
stereoscope, by placing the end of a small book between these 
figures, and letting the other end rest against the nose and fore¬ 
head, thus separating the eyes from each other. If now you 
look intently at the two figures, you will in a few moments find 
them approximate each other, till at length they mingle to¬ 
gether, and you will see but a single dog standing out like a 
statue. The same thing can be shown by mathematical figures. 
Thus, if two figures a a, represented in Fig. 173, be placed in 


\ -» / 


1/ M 

the two apartments of the instrument, on looking into it you 
will sec a single figure, shaped like b. You can imitate the 
stereoscope here also, by placing the end of a book in such a 
way as to cover the middle figure, the other end being between 
the eyes. The two figures will run together, and the union 
will represent the figure of a truncated, four-sided figure, stand¬ 
ing out in bold relief. But such experiments afford only a rude 
imitation of the stereoscope, for in this instrument the separa¬ 
tion between the eyes is entire, so that the effect is produced 
at once. There is no running together of the two figures, but 
the moment that you look into the instrument they are blended 
in one. 

456. The harmony which we have seen to exist in the action 
of the eyes is very wonderful. It must be remembered tli£_t 
the eyes are optical instruments, endowed with self-adjusting 
powers, to accommodate the different distances of objects, and 
the varying degrees of light. And thus must both be just 
alike in all these diversified adjustments, that the images in 
both may correspond. And besides all this adjusting machinery 
inside of the eyes, so delicate and so correspondent in its action 
in both, there is muscular machinery outside, to move the eye* 


FIG. 173. 


























THE EYE. 


305 


Correspondence noi only between the two eyes, but also between their nerves. 

balls in all directions; and in these movements also, as you 
have seen, there is an exact correspondence. All these motions 
for adjusting this complicated machinery within and around the 
eyes, are regulated by the nerves. How astonishing the accu¬ 
racy with which they do this! How exact are the different 
impressions transmitted through them, in producing the various 
degrees, and multiplied combinations of action, in the little 
muscles of these organs! 

457. There is correspondence not only in the machinery of 
the eyes, as optical instruments, but also in that portion of the 
process of seeing which is not mechanical. The nerves of vis¬ 
ion must be exactly correspondent in the two eyes, that similar 
impressions may go from the retina to the brain in both. And 
the correspondence is in this case the more wonderful from the 
fact, that the impressions transmitted are, as you have seen, 
not always precisely alike. How the harmony is preserved in 
connection with this variation is a great mystery. We can 
readily conceive how a single impression can result in the mind, 
from two impressions transmitted to the brain from two images 
which are exactly alike. But we cannot conceive how confu¬ 
sion can be avoided when the images and the consequent impres¬ 
sions are in some measure different. In this connection I will 
notice a peculiarity in the arrangement of the optic nerves. 
They are not entirely separate as they go from the eyes to the 
brain. At one point in their course they unite together, and 
then separate again. In doing so, some fibres from both the 
nerves communicate together, and some cross each other, so 
that a portion of each nerve passes over to the other before 
they go to the brain. Undoubtedly this arrangement has some 
reference to the harmony of action of the two nerves, but we 
know nothing of the way in which it exercises its agency in 
this respect. 

458. The power of perceiving the size, distance, and figure of 
objects, is wholly an acquired power. The case already referred 
to, in which Cheselden restored the sight by an operation, shows 
this to be true. “ When he first saw,” says Cheselden of his 
patient, “ he was so far from making any judgment about dis¬ 
tances, that he thought that all objects whatever touched his 
eyes (as he expressed it,) as what he felt did his skin, and 
thought no objects so agreeable as those which were smooth 
and regular, though he could form no judgment of their shape, 
or guess what it was in any object that was pleasing to him. 
He knew not the shape of any thing, nor any one thing from 





306 


HUMAN PHYSIOLOGY. 


Power of perceiving the size, distance, and figure of objects acquired. 

another, however different in shape or magnitude; but upon 
being told what things were, whose form he before knew from 
feeling, he woulci carefully observe, that he might know them 
again; but having too many objects to learn at once, he forgot 
many of them; and (as he said), at first he learned to know, 
and again forgot a thousand things in a day. At first he could 
bear but very little light, and the things he saw he thought 
extremely large; but upon seeing things larger, those first seen 
he conceived less, never being able to imagine any lines beyond 
the bounds that he saw; the room he was in, he said, he knew 
to be but part of the house, yet he could not conceive that the 
whole house could look bigger.” Every infant, if it could ex¬ 
press its ideas, could give us a narrative of a similar experience, 
in its first lessons in seeing. It is obvious that seeing is a pro¬ 
cess which we learn to do, as really as we learn to talk or walk. 
The confused vision of the infant bears the same relation to 
the accurate vision of the adult, that its uncouth noises and 
awkward motions bear to the adult’s harmonious utterances and 
graceful movements. In order to acquire definite and correct 
ideas of objects, we are obliged to learn how to use those opti¬ 
cal instruments, the eyes. The infant manifestly does not know 
how to use them to any great advantage. He does not at first 
know how to use the muscles that direct the eyes towards any 
object, and there is, therefore, an obvious awkwarduess in their 
movements. As he reaches out his hands towards objects, it 
is plain that he does not appreciate their distances. He reaches 
out for the moon, or any other distant object, just as he does 
for the toy that is held before him. It is by a continued com¬ 
parison of experiences that he learns the sizes, shapes, and dis¬ 
tances of objects. And in doing this, the sense of touch acts 
as the educator of the vision, very much, as the ear educates the 
voice. And even the adult, with all the training which he has 
bestowed upon his eyes, often makes mistakes, especially in rela¬ 
tion to magnitude and distance. There are various degrees of 
skill in seeing; and he is the most skillful seer wno makes the 
fewest of the mistakes referred to. 

459. Let us look now at the means by which we gain the 
experience that is necessary to correct vision. One means is 
the appreciation of the space occupied by objects in the field 
of vision. This is measured by what is termed the visual 
angle —that is, the angle which is formed by two lines coming 
from the extremities of an object, and meeting in the eye, as 
represented in Fig. 174. In this way we get the idea of mag 






THE EYE. 


807 


Visual angle. Distance of objects estimated by their distinctness. 


FIG. 174. 



nitude. But it is manifest that it cannot alone give us this idea 
correctly. It would do so, if all objects were at an equa. 
distance from the eye. But you can see by the figure, that if 
they are at different distances, you must know something of 
those distances, to estimate the magnitude of the objects by 
the visual angle, which they subtend. The arrow at A, B will 
appear just as large as the larger one at A 7 , B', because it will 
occupy the same space a, b on the retina, and subtend the same 
angle. But if you know that the one is nearer to you than 
the other, you make allowance for this in the estimation of the 
size. Your hand, held up to keep the rays of the sun from 
your eyes, would look to you as large as the sun itself, if you 
did not know how near it is to you; and the sun and moon 
appear to us to have about the same magnitude, because we do 
not keep in mind the fact that the sun is ninety-six millions of 
miles from us, while the moon is only two hundred and forty 
thousand. 

460. Another means which we use in getting a correct idea 
of objects by vision, is the degree of distinctness in their lines, 
and shadows, and colors. The fact is learned very early by 
the child, that the nearer objects are, the greater is their dis¬ 
tinctness ; and he makes use of this fact continually in estim¬ 
ating both their distance and their magnitude. He estimates 
the latter less directly than he does the former by this means. 
He makes use of his notion of the distance of an object, gained 
by its degree of distinctness, in forming an idea of its magni¬ 
tude. Many mistakes are made in the use of this means of 
judging of objects. Thus, a very bright light will often appear 
to be nearer than one that is less bright. When the atmos¬ 
phere is very clear, mountains and other objects appear nearer 
to us than they do when the atmosphere is thick and hazy. 

461. Another means of making a correct estimate of the 
distance and magnitude of objects is, comparison with other 





308 


HUMAN PHYSIOLOGY. 


Size of objects estimated by comparison. Muscular sense in the eye. 

objects which are familiar to us. Thus, we get our ideas of 
the size of animals from objects in their neighborhood. The 
artist makes use of this means of communicating ideas of size 
in pictures and engravings. Figures of men are placed near 
large buildings for this purpose. A notion of the great size of 
the elephant is given by placing his keeper at his side. I need 
not multiply instances of this sort. We are not ordinarily 
aware how dependent we are upon such comparisons, in esti¬ 
mating the magnitude of objects. An occasional mistake re¬ 
minds us of it however. For example, I once turned my eye 
suddenly from a giddy height, upon some huts below at a river’s 
side; they appeared to me to be dog kennels, till a man issued 
from the door of one of them, and thus dispelled the illusion, 
by affording me a means of comparison. So complete was the 
illusion, and so sudden was the dissipation of it, that it seemed 
as if there was an instantaneous swelling of dog kennels into 
huts. Every one must have noticed how large the full moon 
appears as he sees it rising, while the higher it rises the smaller 
it becomes to the eye, although it is really at no greater distance 
than it was when it first rose. The reason is, that when it first 
rises you see it in a range with other objects, with which you 
instinctively compare it. And, therefore, it appears larger when 
you see it rising in the direction of some distinct object, as a 
large building, or a high hill, than it does when you see it rising 
over a level plain. 

462. Another means of judging of the magnitude and dis¬ 
tance of objects is, the muscular sense (§ 323) exercised in 
adjusting the eyes in seeing them. Thus, consciousness of 
the amount of muscular action, in passing the eye up and down 
a tall object, helps to give us an idea of its height. So too, in 
looking at near objects, consciousness of the amount of effort, 
in turning the two eyes towards the point looked at, helps us 
to estimate the distance of the object. Commonly we do not 
distinctly think of this effort, because it is so easily made; but, 
if after looking at an object held at some distance from the eyes, 
we suddenly bring it very near, the effort to make the axes* of 
the eyes converge enough to see it distinctly is very manifest, 
producing a straining effect, which, if it be repeated many times 
successively, wearies the eyes. You can discover how very 
dependent you are upon this sense of the convergence of the 

* The axis (plural axes’) of the eye is a line drawn through the centre of the cornea 
and pupil backward through the eye to the central point of the retina. In Fig. 171 th< 
axes are B b, and B b' 





THE ETE. 


S09 


Seeing is in part a mental process. Really complicated and difficult. 

eyes, in accurately estimating comparative distances in near 
objects, by attempting to thread a needle, or nib a pen, or 
snuff a candle with one eye shut. The change in the converg¬ 
ence of the eyes, on looking at objects at different distances, is 
very manifest to us when we observe the eyes of others. We 
perceive thus not only the direction, but the distance of the objects 
at which they are looking. We do this so continually from our 
infancy, that we very early acquire great accuracy in judging, 
at what distance the point is towards which the eyes are turned, 
or in which, in other words, the axes of the eyes meet. 

463. From the facts presented in the few last paragraphs, it 
is obvious that what we include in the word seeing is, to a great 
extent, a mental process. That is, there are certain mental 
efforts which are absolutely essential to correctness in vision. 
Without these mental efforts or processes, we could not see 
things as they are, as it is expressed very properly, but we 
should see them as the boy operated upon by Cheselden did, 
when he first began to see. Seeing is commonly supposed to 
be a very simple process. The idea is, that one has merely to 
open his eyes, and he sees. But, as you have seen, the whole 
process is both a complicated and a difficult one; and in order 
to be able to do .it, the eyes have to go through a course of 
training in the case of every infant, just as was the case with 
the boy whose sight Cheselden restored. We should be con¬ 
scious of this, if we could recollect the experiences of infancy. 
But not being able to do this, it is only when we make some 
extraordinary effort in vision, that we are at all sensible that 
there is any acquired skill in the process. After the training 
which the eyes have in infancy, ordinary seeing is done with 
so much facility, that we are not conscious of any effort either 
bodily or mental. This appears very wonderful, when we con¬ 
sider "that the eyes are two optical instruments, which need, as 
you have seen, a most careful and nice change of adjustment 
continually, to see in different directions, and at different dis¬ 
tances, and that there is also considerable and complex mental 
effort in getting the right impressions from the objects which 
are pictured upon the retina. 

464. But there is another view in which the mental part of 
the process of vision appears strikingly prominent. When it is 
said that images of objects are formed upon the retina, and that 
impressions are transmitted from them to the brain, this is far 
from stating all that is true on that point. Many of the 
images pictured upon the retina do not transmit impressions to 




310 


HUMAN PHYSIOLOGY. 


All images on the retina do not produce impressions in the mind. 

the mind. The sensation of seeing is, therefore, in relation to 
them incomplete—the beginning only of the process is effected. 
This you have seen to be true in the case of strabismus or 
squinting. The faulty eye in this case is not used—the mind 
takes no cognizance of the images formed in it .(§ 453). But 
it is true of ordinary vision also, that the mind takes no cogni¬ 
zance of many of the images formed on the retina. This can 
be verified by a simple experiment. If you hold a finger near 
the eyes (at some ten or twelve inches from them), and a fin¬ 
ger of the other hand at a greater distance, but in the same 
direction, and then look at the near finger, you will perceive 
that the other finger appears double. So, on the other hand, 
if you look at the distant finger, the near one appears double. 
The reason of this can be made clear to you by Fig. 175. The 
two eyes, L and R, being direct¬ 
ed so that their axes converge 
on the object A, the middle 
points of the two images cor¬ 
respond with the middle points 
of the retina in the two eyes, a 
and a'. The images thus cor¬ 
responding in their place on the 
retina, the impressions carried 
from them by the two optic 
nerves to the brain correspond 
also, and so the vision is single. 

But the image of the object B 
is formed in the two eyes, in 
parts of the retina that do not 
correspond, b and b'. They are 
both on the inside of the mid¬ 
dle points, a a', that is towards 
the nose; whereas the outward 
part of the retina in one eye 
corresponds with the inward 
part in the other eye, and vice versa. This you will see to be 
true by recurring to Fig. 171, in which is shown the way in 
which a row of objects is pictured on the retina in the "two 
eyes. There you see that the image of the object A, for ex¬ 
ample, is in the left eye, L, on the inner side of the middle point, 
b of the retina; while in the right eye, R, it is at the outer side 
of the middle point, 6'. In the case of the object B, then, in Fig. 
175, it is clear to you that the images of it in the two eyes are 


FIG. 175. 








THE EYE. 


313 


Some of the images on the retina are not attended by the mind. 

fprnied in parts of tlie retina that do not correspond, and there¬ 
fore, it appears double. 

465. The application of all this to the point in hand you 
can readily see. As the images of all objects in the field of 
vision of the two eyes are pictured on the retina, it is plain, 
according to the facts developed above, that whenever the eyes 
are directed together to any one object, other objects in the 
same direction, but at a different distance,^must make images 
on the retina in the two eyes that do not correspond. We are 
therefore continually seeing double, so far as that part of the 
process of seeing, which consists in the formation of the im¬ 
ages, is concerned. But we are not ordinarily conscious of 
seeing double. How is this ? How is the difficulty (for it is a 
real difficulty in the eyes, as a pair of optical instruments, aris¬ 
ing from the non-corresponding images) remedied ? It is done 
obviously in the other part of the process of seeing, the mental 
part. The mind regulates vision by the varying degrees of 
attention it bestows on objects. Ordinarily it does not attend 
to non-corresponding impressions that come from the non-cor¬ 
responding images, but it attends only to those which are corres¬ 
pondent. As in squinting, it disregards, as you have seen, the 
impressions that come from the faulty eye, so in ordinary vision 
it disregards many of the impressions that come from both of 
the eyes. By an effort of the will it can attend to the impressions 
which it ordinarily disregards. When this effort is not made, 
it disregards them, as we may say, instinctively. To make this 
obvious, I will recur to the experiment with the two fingers, 
held at different distances. When you first attempt the experi¬ 
ment, you do not for the moment perceive that you see one 
finger double, because you change the direction of your eyes 
from one finger to the other, so easily and so unconsciously, 
that you seem to see them both singly at once. But by a little 
mental effort you fix your eyes on one, at the same tim<s attend¬ 
ing to the images and consequent impressions produced by the 
other, and then the experiment succeeds. From all this it is 
obvious that the reason that you do not see very near objects 
double, when looking beyond them to distant ones, or see distant 
ones double when looking at near ones in the same direction, 
is simply that the mind ordinarily attends only to those images 
and impressions which are correspondent, while it with an ha¬ 
bitual instinct disregards those which are not so. 

466. In connection with this subject of the influence of mental 
attention on vision, it is proper to notice the fact, that vision is most 





312 


HUMAN PHYSIOLOGY. 


Point of distinct vision. Minuteness of the images on the retina. 

distinct at the central part of the retina—that part where the axis 
of the eye strikes, as seen in Fig. 171, b, b'. This is commonly 
called the point of distinct vision. The mental attention makes 
use of this point continually. Thus, if we are looking intently 
at a minute object, the eyes are so directed, that their converg¬ 
ing axes meet on the object. So when we are reading, although 
the whole page may be pictured on the retina of each eye, only 
the letter on which the axes of the eyes meet is seen with per¬ 
fect distinctness. And the point of union of the axes moves 
from one letter to another along the lines, so that each letter is 
successively pictured on the central part of the retina. The 
process is so rapid that we are not conscious of it, until 
we take pains to observe what the process is. So, in looking 
at a prospect, the eyes at each moment see some one point 
more distinctly than any other part of all that fills the field of vis¬ 
ion. We are unconscious of this, just as in the case of read¬ 
ing, because the axes of the eyes are so continually moved by a 
slight but exceedingly quick motion from one point to another. 
We in this way take into the central part of the retina so many 
points with such rapidity, that, by a mingling of the impres¬ 
sions upon the mind, we seem to see the whole prospect at the 
same moment, with nearly equal distinctness. The successive 
impressions from the images on the retina, occupy so little time, 
that they appear to be simultaneous, unless we watch the process. 

467. But although some one letter on a page, or some one 
point in a prospect, is at each moment seen with much more 
distinctness than what is all about it, yet there is some vision 
of the page and of the prospect as a whole, of course being 
less distinct the farther it is from the central point. It is pic¬ 
tured as a whole on the retina, and the impression from it as a 
whole goes by the nerve to the brain. The picture is a very 
minute one, as it occupies a small space, and yet it is very dis¬ 
tinct in all its lines, and shades, and colorings. On this point 
Dr. Paley remarks that “ in considering vision as achieved by 
the means of an image formed at '.he bottom of the eye, we 
can never reflect without wonder upon the smallness, yet correct¬ 
ness of the picture, the subtility of the touch, the fineness of 
the lines. A landscape of five or six square leagues is brought 
into a space of half an inch diameter; yet the multitude of 
objects which it contains are all preserved; are all discriminated 
in their magnitudes, positions, figures, colors. The prospect 
from Hampstead Hill is compressed into the compass of a six¬ 
pence, yet is circumstantially represented.” 




THE EYE. 


313 


Our judgment of the motion of objects often erroneous. 

468. We form a judgment of the motion of bodies, in part 
by the movement of the images of them upon the retina. The 
perception of this movement must be exceedingly delicate, for 
even when a body passes over a considerable space, its image 
moves over a very small space on the retina. “A stage-coach,” 
says Dr. Paley, “ traveling at its ordinary speed for half an 
hour, passes in the eye only over one-twelfth of an inch, yet is 
this change of place in the image distinctly perceived through¬ 
out the whole progress; for it is only by means of that per¬ 
ception that the motion of the coach itself is made sensible to 
the eye. If any thing can abate our admiration of the small¬ 
ness of this visual tablet, compared with the extent of vision, 
it is the reflection which the view of nature leads us every hour 
to make, viz : that in the hands of the Creator, great and little 
are nothing.” 

469. Many of our impressions in regard to motion, as we 
look at objects, are erroneous. When we are moving ourselves, 
for example, stationary objects appear to move. As we ride 
rapidly, the objects that we see seem to fly by us. This is 
especially the case, if the motion to which we are subjected be 
an even one, as when we ride in a rail-road car. And if we 
look at distant and near objects at the same time, while the 
near objects seem to fly back, the distant seem to go along with 
us. This is owing to their relative change of position, as can 
be made clear by Fig. 176. Suppose that when at a you see 

FIG. 176. 



27 







814 


HUMAN PHYSIOLOGY. 


Rapidity of succession of images on the retina. How measured. 

two objects, c and d , in the same direction. If you pass rap¬ 
idly to b, the object c appears to have moved backward in rela¬ 
tion to the object, d, while the object, d , appears to have moved 
forward in relation to c ; and the line, d, e, represents the rela¬ 
tive change of positions in the images of the two objects upon 
the retina. 

470. As every object that we see is daguerreotyped, as we 
may say, upon the retina, the rapidity with which these pic¬ 
tures change, and the distinctness with which the nerves trans¬ 
mit impressions from them to the brain, are very wonderful. 
The time required for each transmission is very small—only the 
fraction of a second. The length of time has been estimated 
by experiment. Thus, if it is found that a burning coal, whirl¬ 
ing around at the rate of six times in a second, produces a 
continuous circle of light, but that the circle is broken when it 
whirls round only five times in a second, we know that the 
length of time required for a distinct and separate impression 
is the one-fifth of a second. The same experiment can be 
tried with a wheel. In this case we observe what is the largest 
number of revolutions in a second, that can be made without 
blending the visual impressions of the spokes into one con¬ 
tinuous impression. By such experiments, it has been found 
that the time required for a distinct visual impression varies in 
different individuals, and in the same individual at different 
times, from one-fourth to one-tenth of a second. This differ¬ 
ence in the rapidity of succession of the impressions is of course 
not owing to any difference in the rapidity of the formation of 
the images; for they are formed by the light, and light always 
moves with the same velocity. It must be owing manifestly to 
a difference of facility on the part of the mind, in receiving 
impressions from the images. In other words, the mental ac¬ 
tivity in the use of the optical instruments, the eyes, differs in 
different individuals, and in the same individual at different 
times. If one sees more quickly than another, it is a mental 
quickness. It is a difference analogous to that which we see in 
relation to the use of other instruments of the mind, the mus¬ 
cles for example. Some use these instruments much more 
readily and rapidly than others. We see this in the motions 
of the eyes themselves, and the eyelids also. Some wink more 
quickly than others, and there was wisdom in the decision of 
the blacksmith who dismissed a workman, because he did not 
wink quick enough, and was therefore always getting sparks in 
his eyes. 




THE EYE. 


315 


Thaumatrope. Defenses of the eye. Bones. Cushion of fat. 


471. The blending of impressions in vision, produced by 
rapid motion, has been made use of in the contrivance of an 
amusing optical toy, called the Thaumatrope. In making this, 
you cut a circular card, and make two different figures on its 
two sides. If you attach two silken strings to opposite points 
in its diameter, and then twist the strings, so that when the 
card is left to go free, it will revolve with considerable rapidity, 
the two figures will be mingled together as seen by the eye. 
In Figs. 177 and 178, are represented the two sides of a card, 

FIG. 177. FIG. 17a 



prepared in this way. In this case, the figures as they mingle 
together appear to the eye as a cross. If a bird be drawn on 
one side of the card, and a cage on the other, the mingling of 
the two figures, as the card revolves, will show you the bird in 
the cage. 

There are many other points in regard to the phenomena of 
vision, which it would be interesting to notice. But it would 
make this chapter too long. 

472. The means by which so delicate an organ as the eye 
is protected from injury, are worthy of notice. Observe first 
its situation. Parapets of bone surround it, and receive the 
force of most of the blows that come upon that part of the 
face. Above is the strong arch of bone, forming the lower 
part of the forehead. Then there are the cheek bones, and the 
bones of the nose. Thus, walled in, in all directions by these 
prominences, the eye is seldom hurt, except by a direct thrust. 
And besides being thus protected by surrounding bones, it re¬ 
poses upon a soft cushion of fat, which yields, if the eye be 
pushed backward by violence. Indeed it is thus pushed back¬ 
ward effectually by the muscle that closes the eyelids, whenever 
an impending blow is seen, and it is thus sunk farther back in 
its cushioned recess, amid the projecting parapets, and of course 
receives less of the force of the blow than it otherwise would. 
This muscle, also, by its instantaneous action, prevents manj 








316 


HUMAN PHYSIOLOGY. 


Eye defended by the eyebrows, eyelashes, and lids. The tears wash it. 

light articles from flying into the eye. Such articles are also 
often prevented from entering the eye, by being intercepted by 
the eyelashes. The eyebrow , beside being an ornament, pro¬ 
tects the eye from harm, by preventing the salt perspiration 
from running down into the eye, and irritating it. It acts as a 
thatched roof, projecting from the arch over the eye, and letting 
the perspiration from the forehead evaporate from it, when it 
is small in amount, or drop from it down upon the cheek, when 
it is abundant. The eyelashes also serve to keep the perspira¬ 
tion of the eyelids from entering the eye. The structure of the 
eyelids is such, that the freest motion is allowed, while they 
afford by their firmness considerable protection to the organ. 
They derive their firmness from a fibrous cartilage, which makes 
the body of each lid. You can readily see that this cartilage, 
making an even pressure on the surface of the eye, must often 
prove an effectual defense against direct thrusts. If the weapon 
hit this cartilage, it acts as a firm shield, to ward off the blow 
from the eye behind it. And even that part of the lid which 
is intended by its laxness to allow free motion to the lid, the 
skin, is often an effectual defense. If an impending blow be 
seen, and the eye be instantaneously and forcibly shut, the 
wrinkled skin forms a soft cushion over the eye, and thus not 
only covers it up, but serves materially to deaden the force of 
the blow. 

473. The tear apparatus 
affords the eye material 
protection. The bland tears 
keep the organ properly 
lubricated, so that its con¬ 
stant motions occasion no 
irritation. And if any thing 
gets into the eye, the tears 
are manufactured abund¬ 
antly, for the purpose of 
washing out the intruding 
substance, which is generally 
effected. Fishes have no 
need of a tear apparatus, as 
their eyes are washed con¬ 
stantly by the water in 
which they live. In Fig. 

179 is represented the tear- 
apparatus. The tears are 


FIG. 179. 



TEAR APPARATUS. 




THE EYE. 


317 


Tear apparatus. Oiling the eyelnshes. 

secreted by a small gland, called the lachrymal gland , situated 
at a, in the orbit under the arch of the forehead, and near the 
outer angle of the eye. At b are the ducts which empty the 
tears in upon the surface of the eye on the inside of the upper 
lid. By the constant motions of the organ the tears are diffused 
over its whole surface, and thus continually wash the eye. The 
arrangement for carrying off the fluid is this. It flows through 
a tube, d , e, into the nose. This tube has at its beginning in 
the eye two branches, c, c, which open on the edges of the two 
lids at the inner corner of the eye. These open mouths, that 
drink up the tears as they flow to them, you can very readily 
see. The drain of the eye, which thus conveys the lachryma. 
fluid to the nose, is ordinarily capable of taking care of all the 
tears that the gland makes. But when an uncommon amount 
is made, as in weeping, it cannot receive all the tears, and they 
therefore overflow their banks, the edges of the eyelids. And 
sometimes there is a constant overflow from obstruction of the 
drain by disease. The continual weeping of the eye, when this 
obstruction exists, will give you some idea of the amount of fluid 
which the lachrymal glands make. 

474. Along on the edge of each eyelid are some very small 
glands which secrete an oily substance. This serves two pur¬ 
poses. It oils the eyelashes. It also prevents the tears, when 
they are only in ordinary quantity, from being diffused over 
the edges of the eyelids in the constant motions of the eye. 
This exceedingly small quantity of oily substance suffices to 
keep the tears in the eye where they are needed. There i» 
also a curious provision for directing the tears 
to the mouths of the ducts when the lids are 
closed. When brought together their edges 
unite in such a manner as to form with the 
surface of the eye a triangular channel for the 
tears to run in. This is made clear by the 
diagram in Fig. 180, in which the line b rep¬ 
resents the surface of the eye, and a the edges 
of the lids, showing a section of the canal be¬ 
tween them. 

475. I had intended to notice some of the 
peculiarities of the eyes of different classes of 
animals, but this chapter is already so long that I will notice 
but one — the nictitating membrane in the eyes of birds. 
When not in use it is gathered up in the inner corner of the 
eye. When it is stretched over the organ it is a thin transit 

27* 


FIG. 180. 






818 


HUMAN PHYSIOLOGY. 


Nictitating membrane in the eyes of birds. 


cent membrane. It is very elastic, so that 
as soon as the muscles that sweep it so 
quickly over the eye are relaxed, it flies 
back at once to the corner where it is so 
snugly folded. In Fig. 181 it is represented 
as half way over the front of the eye. In 
Fig. 182 are seen the curiously arranged 
muscles that move it. One of the muscles, 
57 , arises from the ball of the eye at its up¬ 
per part, and running back forms by the 
trunk of the optic nerve a tendon with a 
loop, through which the tendon of the other 
muscle, p, works. This muscle arises from 
the lower part of the ball of the eye, op¬ 
posite to the origin of the first muscle. Its 
tendon, is fastened into the edge of the 
nictitating membrane. It acts through 
the loop as a pulley, and you can see that 
the muscle, g, assists it materially in effecting 
the very quick motions of the membrane. 


FIG. 181. 



FIG.182. 



CHAPTER XVII. 

CONNECTION OF THE MIND AND THE BODT. 

476. In the Chapter on the Nervous System I gave you a 
general view of its functions and its arrangements. You saw 
that it is to the mind the grand means of communication with 
the world of material and immaterial things around it. In the 
Chapters on the Senses and the Organs of Locomotion, we have 
considered the modes in which this communication is maintained, 
through organs subordinate to the nervous system. And you 
have seen that through the senses all knowledge of external 
things is communicated to the mind, where it is used as the 
material of thought and reflection and feeling; while, on the 
other hand, through the muscles the mind produces all its im¬ 
pressions upon the things and beings on which it acts. You 







CONNECTION OF THE MIND AND THE BODY. 319 


The brain the organ of the mind. Facts which prove this. 

are now therefore prepared to look more thoroughly into the 
connection which the nervous system establishes between the 
mind and the body, and to observe some of the higher and more 
intricate phenomena which result from it. It is to views upon 
these points that I shall devote this and the following chapter. 

477. The brain is the organ of the mind. In this life there 
can be no mental manifestations except through the agency of 
this organ. The mind and the brain always act together as one 
thing. This is manifest in regard to motion and sensation. It 
is equally true of thought. The mind can think and excite 
motion in the muscles only through the brain. The proofs of 
this are various and abundant. If a man by a blow upon his 
head have a portion of the skull driven in upon the brain, so as 
to press upon it considerably, all sensation and power of motion 
are suspended. His mental connection with the world around 
him is completely cut off. And not only so, but all mental ac¬ 
tion is arrested. The mind, thus shut in from the world around 
by the suspension of sensation, does not go on to act indepen¬ 
dently of the compressed brain. The man does not think; for 
if thinking did occur in such cases, there would occasionally be, 
as after dreaming, some recollection of what passed through the 
mind, after the pressure is taken off from the brain by the tre¬ 
phine and elevator of the surgeon. He lives, because the invol¬ 
untary muscles, connected by their nerves with the top of the 
spinal marrow, (§ 229,) which is uninjured, carry on the breath¬ 
ing and the circulation. But though he lives, he is not now a 
moving, or a sentient, or a thinking being. His mind is as 
dormant as life is in a state of hibernation. 

478. The same state of things occurs in apoplexy, and in the 
senseless state which accompanies most convulsions. And it 
may be remarked, that the degree of the suspension of the 
mental functions depends upon the degree of effect produced 
upon the brain. If, for example, in the case of injury, the 
pressure of the bone driven in upon the brain be not very great, 
the suspension will be partial; but if the pressure be considera¬ 
ble the suspension will be complete. 

479. The dependence of the mind upon the brain is mani-» 
fested in a great variety of diseases. The delirium of fever and 
of inflammation of the brain, and insanity resulting from chronic 
disease in this organ, show this absolute and inseparable con¬ 
nection of the mind with the material organization in our present 
state of being. We sometimes see the mind gradually blotted 
out by the progress of disease in the brain, so that a man of 





320 


HUMAN PHYSIOLOGY. 


Insanity a disease of the organization. Situation of the brain. 

even high mental powers becomes a drivelling idiot. So, too, 
a bad formation of the brain, or early disease of this organ 
often prevents mental development. Insanity is always the re¬ 
sult of disease in the organization. This is so even when it is 
produced by moral causes acting directly upon the mind. The 
insanity in such a case is an indirect effect—the organization 
affected by the mind is thrown into a diseased state and reacts 
upon the mind, influencing its manifestations. “If the mind 
thus acted upon were a spirit, separated from the body, the 
result would be merely the feelings, which the motives applied 
would naturally produce, and not the unnatural feelings of 
insanity. It is not strictly proper then to speak of a ‘ mind 
diseased.’ Let me not be understood to mean that mental de¬ 
rangement in every case is to be attributed to disease that leaves 
such palpable traces, that the dissecting knife would reveal it if 
death were to take place. There are diseased operations of the 
body, that are hidden from our view—so hidden, that they not 
only leave no traces, but often develop no characteristic bodily 
symptoms.”* I shall recur to this subject of the dependence 
of the mind upon the brain in another part of this chapter, and 
shall endeavor to point out definitely what are the teachings of 
physiology, of our consciousness, and of revelation respectively 
in regard to it. 

480. Observe for a moment the situation and the immediate 
connections of the brain, the organ of the mind. Its situation 
in the human structure is appropriately a commanding one. It 
is fitly placed at the summit of the structure, inclosed by that 
noble dome which I described to you in the Chapter on the 
Bones. And then observe that in its immediate neighborhood 
are the organs of four of the senses, sending their messages 
continually to the mind. Especially you notice that under the 
jutting arches of the front of the dome are the ever-moving 
eyes, looking out from their elevated place of observation; and 
at the sides of the base of the dome are the halls of audience, 
ever open and ready to transmit the messages that come to the 
soul through the vibrations of the air. And there, too, in the 
very front of this habitation of the mind is the face, indicating 
by the delicate, quickly changing play of its muscles the thoughts 
that are at work within. And lastly, there is the mouth, the 
outlet for the voice, the chief agent of the outward manifesta¬ 
tions of the mind. Here then are clustered together in this 


* “Phy»ician and Patient,” page 292. 





CONNECTION OF THE MIND AND THE BODY. 321 

Rapidity of communication between the mind and the body. 


small space, in the immediate neighborhood of the mind’s hab¬ 
itation, its principal instruments of communication with the 
world around. When we are listening to eloquence, whether 
it be in the public assembly, or in the social circle, or in the 
more private intercourse of friendship, and observe, as the rich 
tones proceed from the mouth, the elevated and changeful ex¬ 
pressions of the countenance, we are impressed with the idea, 
that, if it be the mind which constitutes the image of God in 
man, the face of man thus situated in the front of the mind’s 
habitation, is the fitting outward emblem of that image. 

481. It is interesting to observe how exceedingly rapid are 
the communications of the mind with the different parts of the 
body. Notice what the process is, or rather what the processes 
are, when you withdraw your hand from any thing that hurts it, 
as heat for example. An impression is produced upon the ex¬ 
panded nerve in the part—this impression is sent along the 
nervous tubuli to the brain—the mind there receives the im¬ 
pression—the mind in return communicates an impression to 
the brain—this impression goes by another set of nervous tubuli 
to the muscles—they act, and the hand is withdrawn. If it 
took as long to do all this as it has for me to describe it, the 
hand would be very thoroughly burned before it is drawn away. 
The same set of processes is gone through with, when in ex¬ 
ecuting music, either with the voice or an instrument, a mis¬ 
take is immediately heard and corrected. And so of other 
cases. 

482. In the Chapter on the Muscles I spoke of the great va¬ 
riety in the motions of the body. In executing these motions 
the individual commonly knows nothing of the muscles with 
which he does it. Even the anatomist, who is familiar with the 
situation and arrangement of the muscles, seldom thinks of 
them while he works them in the production of different mo¬ 
tions ; and if he does think of them it affords him no assistance 
in their use. Great skill can be acquired in the use of the 
muscles, without any knowledge in the individual of the fact that 
he has such organs. In muscular action men commonly move 
a machinery of which they know nothing. They have only to 
will any particular motion, and the nerves are so arranged at 
one end with the muscular fibres that will do it, and with the 
brain at the other, that the message from the mind goes to 
exactly the right fibres, and the result is produced. For the 
infinite variations of motion in the body what complicated and 
intricate arrangements are needed! These variations, it is to 




322 


HUMAN PHYSIOLOGY. 


Skill in the use of the muscles. Variety in their action. 


be remembered, do not result merely from combinations of 
movements, but are rendered vastly more extensive from the 
varying degrees of contraction in the muscles. If each muscle 
always acted just so much and no more, there would be even 
in that case great variety of motion, from its combination in 
various ways with other muscles. But the variety is made to 
be endless from the endless variation in the degree of their con¬ 
traction. And for each one of these variations, both in degree 
and combination of action, there must be a different message 
sent from the mind along the nerves. In every motion the 
muscles that produce it must, so to speak, be told to act, and not 
only so, but they must be told just how far to act. In motions 
that are very compound, and at the same time exceedingly del¬ 
icate in their variation, the accuracy and variety of the mes¬ 
sages thus sent from the brain along the nerves are not only 
wonderful, but are beyond our conception. We realize this 
fully, when with the views above expressed in the mind, we 
watch a skillful balancer, as he executes his endlessly varied but 
exact movements. So, too, when we hear from Ole Bull’s one 
violin such a mingling of sounds, that we feel that there must 
be a half a dozen violins played upon at once, how inconceivably 
rapid and numerous and complicated must be the messages that 
fly from his brain along the nerves to the muscles, and yet there 
is not a failure in one of them—not a fibre that does not con¬ 
tract at the right moment, and in the right degree! 

483. The use which the mind makes of all the machinery of 
the senses and of the organs of locomotion does not come to it 
at the outset. It comes by training, and in some cases by very 
long training. The child at first uses its muscles bunglingly. 
It does not see or hear skillfully. It knows nothing at the first 
of the colors, or shapes, or distances of objects. It knows nothing 
of the direction or distance of sounds. It has all these things 
to learn. And for this purpose the organs of sense and the 
muscles are put into exercise at once, and the child begins its 
long process of learning on the day of its birth. Few have any 
conception of the amount of knowledge which is acquired in 
the first of the child’s life. He is born not only with absolutely 
no knowledge of the world of things around him, but he has 
no skill in the use of the instruments, the muscles and the 
senses, by which he is to obtain his knowledge. These give 
him at first no very definite information; but by the constant 
exercise of them, and by comparisons between the reports of 
the different senses he soon adds rapidly to his stock of knowl- 







CONNECTION OF TIIE MIND AND THE BODY. 323 


Learning to use the muscles. Their action at first aimless and awkward. 

edge, and becomes skillful in the use of liis means of gathering 
it. But let us see a little more particularly liow this is done. 

484. I will speak first of the progress of the child in learning 
how to use his muscles. When he first puts them into action 
you see that he has no skill in using them. The action is aim¬ 
less and awkward. You see in his movements none of that 
native grace of which so much is said. This is to be acquired, 
and all that is native about it is the power of acquiring it. He 
learns to execute very many motions before he comes to that 
complicated movement of so many muscles, creeping, and then 
the no less complicated but more difficult one of walking suc¬ 
ceeds. How awkwardly he does this in his first attempts to 
preserve his balance, and how many failures must he encounter 
before he can perform this motion even decently well! The 
same thing can be said of learning to talk or to sing, for this is 
but a training of the muscles. It is thus gradually that all the 
voluntary muscles become educated. It is true even of the 
muscles of the face. At the first how expressionless ordinarily 
is the face of a child. You see nothing of those delicate move¬ 
ments of the muscles which in after years express every varying 
shade of thought and feeling. When he cries there is an awk¬ 
ward over action of the muscles, as represented in Fig. 183. 

FIG. 183. 



He learns to use these muscles partly at least, by imitation. 
His first lesson ordinarily is in smiling, which he soon learns 
by imitating the smile of his mother. But even this, simple 






324 HUMAN PHYSIOLOGY. 

Skill in the use of the senses and the muscles. Comes later in man than in animals. 


as it is, he does awkwardly at first, and he must go through a 
long process before he can master all the capabilities of ex¬ 
pression in these little muscles. 

485. Skill in the use of the muscles varies quite as much as 
any other acquirement in different individuals. It is wonderful 
in the juggler, the rope dancer, the skillful player on a musical 
instrument, and the accomplished singer. You will have some 
conception of what education can do for the muscles, if you 
contrast the awkward balancing of the child in walking with 
the agile and delicate balancings of the rope dancer, or the 
aimless and uncouth movements of the infant’s hands with the 
rapid and varied execution of the player on an instrument, or 
the monotonous and coarse sounds uttered in a child’s first 
attempts at singing with the varied melody of a skillful singer. 

486. The senses are educated as well as the muscles. As 
you see an infant reaching out his little hands awkwardly with 
his unskilled muscles towards an object, it is manifest that he 
knows not at what distance the object is from him, and that 
he does not readily adjust his eyes to its distance, so as to see 
it clearly. He after a while by practice acquires the power of 
doing this. The same may be said of hearing. The little 
muscles which I described to you as so nicely adjusting the 
eye for seeing at different distances, and the ear for hearing 
various notes of sound, require training, just as the muscles do 
with which we walk or talk. 

487. It is a singular fact that most other animals are born 
with so much more skill in the use of the muscles and the 
senses than man. While man is “ in the nurse’s arms,” the 
chicken,'for example, walks about as soon as it is hatched. 
He does it at first awkwardly, it is true, but he soon learns all 
that is to be learned about it. He is assisted materially, it is 
to be remarked, by the fact that his feet spread out over so 
large a space, that he has no hard lessons to learn in balancing 
as the child has. But this is evidently not all the difference. 
If it were, the child should be able to creep at the first, or even 
walk on its hands and feet, for in performing these motions 
there is no difficulty in supporting the centre of gravity. The 
Samp difference exists also in regard to the senses, for the 
cjhicken eeems tp understand distances at once. As it runs 
about tp pick up its food it rpakes no mistakes on this score. 
But while man is thus at the first the most helpless of animals, 
in regard to both his muscles and his senses, by his process of 
learning he ultimately acquires vastly greater f^nge and va- 




CONNECTION OF THE MIND AND THE BODY. 325 


The senses and the muscles mutual teachers. Exemplified. 

riety of motion than other animals. And the same thing can 
be said of his acquirements through the senses. 

488. The senses and the muscles are mutual teachers iu 
this education which I have described. Thus, in singing, the 
accuracy of the sense of hearing in estimating sounds is ac¬ 
quired through the action of the muscles of the voice while 
the ear is listening. And on the other hand, skill in executing 
sounds is acquired by these muscles under the tuition of the 
ear. The dependence of the senses upon the muscles is not as 
absolute, however, as that of the muscles upon the senses. 
The ear can be trained in the accurate appreciation of sounds 
without any corresponding exercise of the muscles of the 
voice, though the two processes are ordinarily to a greater or 
less extent connected, and are corrective of each other. But 
even when the ear is trained without any aid from the mus¬ 
cles of the voice, the training is in some measure a train¬ 
ing of muscles. For, as you saw in the Chapter on the Ear, 
§ 415, there are certain little muscles that regulate the tension 
of the drum of the ear, which undoubtedly go through a pro¬ 
cess of training when we are learning to distinguish accurately 
between different notes of sound. While the dependence of 
the senses upon the muscles is thus a partial one, the depen¬ 
dence of the muscles upon the senses is, on the other hand, 
complete. Although the muscles have a sense of their own, 
a muscular sense, as Bell calls it, this is not adequate to be 
their sole guide in action, but it serves as a mere auxiliary in 
this respect. This absolute dependence of the muscles upon 
the senses is very strikingly shown in the fact, that the deaf 
and dumb are dumb simply because they are deaf. The voice 
in them has no teacher. The muscles which regulate the ten¬ 
sion of the vocal ligaments, and those which articulate the 
voice do not act, because, as stated in the Chapter on the Voice, 
§ 400, they have no guide in their action. 

489. Although I have spoken of the education of the mus¬ 
cles and the senses, this language is not strictly correct. For 
the education is an education of the mind that operates through 
these muscles and senses. It is the training of the mind in 
the use of these instruments. This is very clearly shown in 
cases of idiocy. In these cases the defect in talking is pro¬ 
portioned to the mental deficiency. It arises from an inca¬ 
pacity on the part of the mind in using its instruments, the 
muscles and the apparatus of the senses, and not from any 
defect in the construction of these instruments. The larynx 

28 




326 


HUMAN PHYSIOLOGY. 


The involuntary muscles not educated. Why. 

and the articulating organs of the voice are perfectly well 
formed in the idiot, as I have stated that they are in the deaf 
mute. While, in the case of the deaf mute they are not used 
at all as vocal organs, because the mind, through the absence 
of hearing, has no power of regulating them; in the case of 
the idiot they are used to a limited extent, and in a very 
bungling manner, because the capability of regulating them is 
limited by the deficiency of the directing intellect. And what 
I have said of the muscles of the voice in the idiot is equally 
true of the muscles of the face. There is no defect of con¬ 
formation, nor is there any lack of lustre in the eye, as is 
commonly supposed. The limited range of expression and its 
awkwardness arise from an incapability on the part of the 
mind of using the muscles of expression with facility and skill. 
The muscles have an incompetent teacher, and so learn to do 
but little, and do that little bunglingly; or, to speak more 
correctly, the deficient mind is not capable of learning to use 
them properly. 

490. The education of the muscles does not extend to those 
which are involuntary. Though respiration, for example, is a 
very complicated act of many muscles, these muscles require 
no education to do their part skillfully. We have no need to 
superintend them, for their constant action is secured by an 
arrangement for nervous influence which is independent of the 
mind, as stated in the Chapter on the Nervous System. So, 
while the mind sleeps, or when it is locked up in the stupor 
of disease, these muscles continue to perform their duty, as 
well as when we are awake. The same substantially can be 
said of the muscles which perform the act of swallowing. Al¬ 
though this is a very compound, and, mechanically considered, 
a very difficult act, as shown in the Chapter on Digestion, § 78, 
it is performed as well in the first hour of the child’s life as it 
is at any future period. The muscles that execute it need no 
training. And yet it is only after long and diligent training 
that the purely voluntary muscles, as for example those of the 
hand, execute movements which are no more complicated and 
difficult. The reason for this difference is obvious. The move¬ 
ments which are performed by the involuntary muscles, such 
as breathing and swallowing, are immediately essential to the 
preservation of life, and it is therefore necessary that they 
should be well executed from the first. Their perfect action is 
therefore secured by a nervous arrangement, which is indepen¬ 
dent of the mind. The voluntary muscles, on the other hand, 




CONNECTION OF THE MIND AND THE BODY. 327 


Association of action in the muscles without mental action. 


instead of being devoted, like the involuntary, to the main¬ 
tenance of life, act as the instruments of the mind, and there¬ 
fore the mind acquires the power of using them skillfully by 
dint of long-continued training. 

491. In the education of the muscles, it is to be observed, 
that although during the process of learning the mind takes 
distinct cognizance at first of every movement, it after a while, 
as the education becomes complete, takes little or no notice of 
many of the movements, except when some error occurs, or 
some obstacle arises. Thus, when one is learning to sing or 
play a tune, the mind at first through the ear takes a definite 
and distinct notice of every sound, and makes a palpable ex¬ 
ertion in every movement. But after the tune is learned, this 
ceases to be the case, and the movements seem to be associated 
together, in some measure independently of mental action. So 
in learning to walk the child notices each of his movements 
very distinctly. But when he has fully learned, but little 
thought seems to be expended upon the motions, except when 
some obstacle appears which interrupts their regular succession. 
When one walks in a reverie, the mind is most of the time 
wholly abstracted from the associated movements which make 
up the compound act of walking. In learning to read the 
child makes a distinct mental effort in regard to each letter, 
resorting to every aid which will help to make the effort a 
successful one, even to the putting the finger on each letter as 
he looks along the line. But as he becomes more and more 
skilled, the association of action of which I have spoken comes 
more and more into play. I will refer you to a partial expla¬ 
nation of the facts above alluded to, given in § 262, in the 
Chapter on the Nervous System. 

492. It has been stated in § 325 and § 476 that the mind 
receives impressions only through the senses, and imparts 
them only through the muscles. These act as the instruments 
of the nervous system, the senses being the inlets and the 
muscles the outlets of communication. And it has been gen¬ 
erally considered as a settled point, that these are the sole 
channels through which the interchange of thought and feeling 
is effected in our present state of being. But it has been pre¬ 
tended that other mysterious modes of communication have in 
these latter days of progress been discovered. The phenomena 
presented by animal magnetism , as it is called, are claimed by 
some to demonstrate, that there is in some cases a peculiar 
means of communication, distinct from those which are usually 





328 


HUMAN PHYSIOLOGY 


Animal magnetism. Simple tests expose it. 

employed. It has been fancied that something analogous to 
magnetism is the medium of connection in such cases, and 
hence the name of animal magnetism. Through this medium, 
it is asserted, that thoughts and sensations pass from one person 
to another, independent for the most part at least, of the ordi¬ 
nary conditions on which communication depends. The phe¬ 
nomena have been presented at different times under different 
phases, and the theory framed to account for them varies 
somewhat from time to time, according to the varying char¬ 
acter of the phenomena, and the tastes and imaginations of 
the believers in this so called science. Amid all the various 
forms which it has thus assumed, with its corresponding di¬ 
versity of names, one thing has always been true of it, viz., 
that whenever any efficient tests have been applied, it is shown 
to be a large superstructure of falsities built upon a very few 
facts. And in view of the uniform results of these tests, we 
may confidently say, that as yet there has been no satisfactory 
proof, that there are any other channels of mental communi¬ 
cation, than the ordinary ones furnished by the senses and the 
muscles. Most minds are bewildered by the strange, and some¬ 
times inexplicable things, which appear in the exhibitions 
which they witness, and are ready to adopt any plausible ex¬ 
planation which may be offered. But some simple yet search¬ 
ing tests have thus far, whenever applied, always sufficed to 
expose the delusion. 

493. In illustration of the manner in which these tests de¬ 
molish the lofty pretensions of this so called science, I will 
give a single example. The exhibitor asserted that whatever 
was in his mind, realized distinctly and vividly, had its image 
in the mind of the subject whom he magnetized, by means of 
the peculiar connection thus established between them. Any 
decided sensation, therefore, which he felt, the subject felt also; 
and if he fixed his thoughts upon any thing, the subject thought 
of the same thing. I observed that whatever was said by the 
subject, in relation to any sensations or thoughts in the opera¬ 
tor, was generally in reply to questions on the part of the 
operator himself. And as these questions were sometimes 
repeated in various forms before correct answers could be ob¬ 
tained, I suspected that the information requisite for the answers 
was communicated to the subject in this way. I, therefore, 
proposed to the exhibitor to try some experiments without 
questions , as these, according to his theory, were clearly not 
necessary; for, if there were such a channel of communication 





CONNECTION OF THE MIND AND THE BODY. 829 


Mental phenomena of animal magnetism. 

between liis mind and that of his subject as he asserted, the 
aid of the voice was not required. The proposition was man¬ 
ifestly so fair an one that he could not refuse to comply with 
it. But his experiments performed in this way failed altogether, 
and the audience, caring less for a strict search for truth than 
for the continuance of their amusement, showed little relish 
for the interruption, and the pseudo-scientific exhibition went 
on. I applied other tests as I had opportunity, which developed 
the evidence of imposture here and there in the exhibition, and 
though many sober and intelligent citizens were deluded with 
the belief that they had enjoyed a rational and truly scientific 
amusement, I had no doubt that the whole was a piece of 
jugglery. There was one feature in the exhibition, which of 
itself was enough to condemn it as a ridiculous imposture. The 
operator claimed to have a sort of absolute control over the 
subject, so that at will he could hold him in a connection with 
himself so insulated that no impressions could be imparted to 
him by any other person, and yet could dissolve this connection 
and put him into connection with some one else, with as much 
facility as a locomotive can be switched off from one track on to 
another. And ridiculous as this shifting of mental connections 
is, this was quite as successful with the audience as any part 
of the exhibition. 

494. Some of the phenomena presented in the exhibitions of 
animal magnetism afford interesting illustrations of the influ¬ 
ence exerted upon the body through the mind. The mental 
influence, exerted by the operator upon his subject, often causes 
a condition of the nervous system, which is analogous to som¬ 
nambulism, or to some of the forms of hysteria. The manip¬ 
ulations practiced, the looking the subject intently in the eye, 
the holding of a piece of metal in the hand with the eye fixed 
upon it, and other expedients, help to produce the impression 
in the mind of the subject, that a mysterious and resistless in¬ 
fluence is coming from the operator upon him, and is stealing 
over his system. It is not strange that this should occasion 
such physical results as we often see, when the mind and the 
nerves are very susceptible. This is the simple explanation of 
all that is positive in what such exhibitions present to us. There 
is no such thing as a magnetic influence, and animal magnetism 
is a misnomer. 

495 . The state of nervous system often produced is not in¬ 
consistent with imposture any more than hysteria is. As in the 
nervous states exhibited by this disease there is often a strange 

28* 





330 


HUMAN PHYSIOLOGY. 


Alliance to hysteria. Suggestive influences. 

perversion of the moral mingled with that of the physical, so 
there is also in the state produced by the mental influence of 
the magnetizer. Accordingly his most available subjects are 
women found here and there in every community, who, through 
this mingled moral and physical perversion, have acquired a 
permanently morbid state of mind, that makes them like to be 
thus petted, and to be the wonder of a gaping multitude. There 
is often in the exhibitions of animal magnetism self-imposition 
at the same time that there is imposition upon others. In the 
case of travelling exhibitors there has always been collusion 
enough to stamp the character of jugglery upon the exhibition. 
And in other cases, where both the operator and the subject 
are honest, there is delusion in both, and they impose not only 
upon themselves, but upon each other, as well as upon those 
that witness the performance. 

496. One of the peculiarities of the state of somnambulism 
which is induced by the magnetizer, is the ready obedience of 
the mind of the subject to suggestive influences. It is alive to 
any suggestions which come from the mind to which it supposes 
itself bound by a magnetic spell, and is often in fact shut up to 
influences from that source alone, so as to be insensible to in¬ 
fluences from any other quarter. The somnambule is possessed 
with one idea, and that an all-absorbing one, because invested 
with such mystery. His insensibility to all that is not in ac¬ 
cordance with this idea is to be accounted for in the same wav 
that we account for the fact, that a wound received in battle 
is often unfelt till the excitement of the battle is over, and other 
similar facts, as alluded to in § 226. This state is often quite 
successfully imitated by impostors; and sometimes there is a 
mixture of a partial real somnambulism with imposture, similar 
to that which occurs in the case of the hysterical condition. 
Of course when this mental connection is so easily shifted from 
the operator to bystanders as was described in § 493, there must 
be sheer imposture. Whether there be full somnambulism alone, 
or this in a partial degree and mingled with deception, the in¬ 
fluence of the principle of suggestion is very apparent. Nothing 
can be done without questions. Leading questions suggest 
ideas to the mind of the subject, and an audience led on by 
love of the marvellous and the exciting, are readily satisfied by 
the coincidences that occur in the exhibition, while the failures 
are disregarded and forgotten. 

497. In the state of somnambulism induced artificially by 
the so-called magnetizer, as well as in that which occurs from 





CONNECTION OF THE MIND AND THE BODY. 331 


Clairvoyance a false pretension. Little that is true in so called animal magnetism. 


othe- causes, there is often an exaltation of the powers of the 
senses. Thus, sometimes a somnambule can read through en¬ 
velopes of even many thicknesses, from an exaltation of the 
sense of vision.* But all pretensions to reading through bodies 
that have no pores or interstices, as metallic substances, or to 
reading from other parts of the body, as the pit of the stomach, 
or the back of the head, are impostures. So too are all the 
pretensions to seeing what is going on in other places, or inside 
of the body. This clairvoyance, as it is called, has precisely 
the same claim upon our confidence that fortune telling has, 
and no more. Real searching tests have always sufficed to ex¬ 
pose its imposture. 

498. I have introduced the above views of what is generally 
called animal magnetism, in order that you may be prepared to 
apply the proper tests, whenever such popular delusions claim 
your confidence. I have introduced them, also, because, what¬ 
ever real phenomena do appear in the exhibitions presented to 
us under this name, afford some interesting illustrations of the 
influence of the mind upon the body. They add another chap¬ 
ter to our view of the mysterious connection of the physical with 
the spiritual, secured by means of that wonderful apparatus, the 
nervous system. It is from this consideration merely that they 
claim the attention of the physiologist. The so-called animal 
magnetism, when thoroughly sifted is dissipated, and there are 
left as a residuum only a few phenomena, which offer nothing 
particularly new, but are chiefly interesting from their analogy 
to phenomena with which we were already familiar. And its 
boast of the discovery of a new medium of mental communica¬ 
tion is, as you have seen, entirely groundless. 

499. In the Chapter on the Nervous System I spoke of the 
different offices of the different central organs of this system. 
The brain, as you have seen, is more especially connected with 
the mind, and is the great instrument through which mental 

* Many of the statements, however, of such cases, could have been found to be 
false if the proper tests had been applied. The failure in testing, so common in these 
cases, I will exemplify by a single case, which made some noise in its time. It is a 
case reported bv Col. Stone in his famous pamphlet. He gave the clairvoyant, a 
sealed packet with a very odd sentence in it, wnich she read, as the Colonel sup¬ 
posed, without opening it. But how did he know that she did not open the packet 1 
Simply because she returned it. to him a day or two after apparently in the same 
state as he gave it to her, accompanied with a copy of the sentence contained in 
it. This he considered good proof, but it is defective in its most essential point. 
If she could read the packet without opening it, why did she not do it in his pres¬ 
ence 1 There is not a particle of evidence that any one saw her do it. The true 
test was an easy one, but it was not applied. There is such a thing as skill in open¬ 
ing seals and replacing them so as to avoid detection, and until we have proof that 
this was not done we are not called upon to believe that the clairvoyant read through 
the envelopes. 







332 


HUMAN PHYSIOLOGY. 


Offices of the cerebrum and cerebellum. 


manifestatioris are made. But it is only a certain part of tlia 
brain, the cerebrum , a, Fig. 72, that has this special connection 
with the mind. The cerebellum . b, Fig. 72, it is supposed, is 
especially devoted to the motions of the body, for it is found in 
animals that it is developed in proportion to the range and va 
riety of motion. From extended observations on this point in 
comparative anatomy there seems to be good reason to conclude, 
that the cerebellum is the great central apparatus for combining 
the various compound motions of the body. It is uniformly 
found to be larger in those animals that have great complica¬ 
tion in their muscular movements, than in those in which these 
movements are of a simple character. Thus, in animals whose 
most complicated motion is walking, as the hoofed quadrupeds, 
the cerebellum is much smaller, than in those animals that climb 
and that take hold of things with their paws. In man it is 
much larger than in any other animal, for he walks erect, and 
thus brings into action a very large number of muscles in this 
delicate balancing movement (for such it is), and then, in the 
individual parts of the body, especially the hand, he executes a 
great range of very complicated movements. It is more devel¬ 
oped in monkeys and apes than in any other of the inferior 
animals, because, with their capability of extensive variety of 
posture, and their power of seizing objects with their extremi¬ 
ties, they obviously come nearer to man than any other animal 
in the varied combination of their muscular action. 

500. The conclusions, thus arrived at by comparative obser¬ 
vations in animals have been confirmed by experiments. It has 
been found by physiologists, that if the cerebellum be removed 
in an animal, with as little disturbance as possible to other parts, 
although the sensibilities remain, and motions are performed, 
the power of combining muscular actions in definite compound 
movements, such as flying, walking, <fec., is lost. 

501. These conclusions have also been to some extent con¬ 
firmed by observation of the phenomena of disease. The testi¬ 
mony from this source, however, has not as yet been very decided 
for two reasons. First, because disease in the brain is not apt 
to be confined to one portion of the organ. And secondly and 
chiefly, because we have not had a sufficient number of observa¬ 
tions of cases on this point. It has been observed, however, in 
some interesting cases of chronic disease in the cerebellum, that 
deficiency in the performance of the compound movements of 
the body was a prominent symptom. An unsteadiness of gait 
was remarked in these cases. The negative testimony which 




CONNECTION OF THE MIND AND THE BODY. 333 


Gray part of the cerebrum proportioned to the intelligence. 

disease gives us in regard to the office of the cerebellum is very 
conclusive. The mental phenomena of disease, when it is fast¬ 
ened upon this particular portion of the brain, show that this is 
not that part of the organ where the thinking is done. 

502. It is chiefly, as you see, by observing the different de¬ 
velopments of the nervous system in various animals, in con¬ 
nection with the different functions performed by this system, 
that we can discover the uses of its different parts. In pursuing 
observations of the animal kingdom in this way, we find a more 
and more complicated nervous apparatus, as we proceed from 
the lower animals up to man. We find part after part added, 
and with every addition of a part we find new functions. And 
as we study any particular part in relation to the functions 
which appear as connected with it, we see that these functions 
are prominent in proportion to the amount of the development 
of the part. Thus, as before stated, we find the size of the 
cerebellum is in proportion to the variety and complication of 
motion in the animal, while that of the cerebrum is in propor 
tion to the amount of intelligence. And in relation to the 
cerebrum itself we find that the amount of intelligence depends 
on the amount of its gray portion, the vesicular substance. In 
man, therefore, this part of the cerebrum is very much greater 
than it is in any other animal. It is the difference in the amount 
of the gray substance which constitutes the grand distinction 
between the brain of man, and that of any of the higher orders 
of animals, for in all other respects his brain differs very little 
from theirs. 

503. In looking at representations of the brain, as in Fig. 74, 
it would seem at first view that the gray substance, the working 
part of the cerebrum, is much less in amount than the white 
portion, which serves only for transmission. But this is not so. 
The eye is deceived, because the white substance is all together 
in one central mass, while the gray substance is spread out in 
an external layer. This is very plainly illustrated by Fig. 184. 
Here the area, a , contained in the inner circle, strikes the eye as 
being larger than the area, 5, included between the two circles, 
and yet these areas are precisely equal. 

504. Observe for a moment in this connection the concurrent 
evidence, by which we determine what the function of the gray 
substance of the brain is. It comes from two sources. The 
first is that which is furnished to us by the structure of the cere¬ 
brum. As stated in § 206 and § 232, the gray portion is 
made up of cells, while the white portion is composed of tubuli. 




334 


HUMAN PHYSIOLOGY. 


Quantity of the gray substance. Phrenology considered. 


FIG. 184. 



These tubuli are such as we find in the nerves, and in fact are 
continuous with them. We very properly infer, therefore, that 
as the nerves serve only for transmission, the white part of the 
brain does the same. Is has, therefore, nothing to do with the 
thinking, and yet this we know from other facts, (§ 477 and 
499,) is done in some part of the cerebrum. So we infer 
necessarily that it must be done in the gray substance. And 
here, to confirm the truth of this inference, comes in one other 
source of evidence, viz., the comparison between different ani¬ 
mals in regard to the correspondence between the amount of 
the gray substance and the amount of intelligence. This I re¬ 
marked upon in § 502, and need not dwell upon it farther. 

505. This dependence of the mental faculties upon the gray 
substance, the outer part of the brain, seems to give some coun¬ 
tenance to the doctrine of phrenology. But there is no evidence 
from an examination of this substance that it is arranged at all 
in separate organs, as instruments or seats of different faculties. 
And all the facts which have been collected in regard to the 
external conformation, as indicating the comparative prominence 
of different organs with their faculties, go to show, when properly 
examined, that the mapping out of the brain which phrenology 
does so definitely is altogether a fiction. The question in re¬ 
gard to this is wholly a question of evidence. For although 
we can see no division of the cortical substance into organs, yet 




CONNECTION OF THE MIND AND THE BODY. 335 

Observations opposed to phrenology. 


if the pretensions of phrenology in regard to the results of the 
external examination of heads are well founded, we must ac¬ 
knowledge such divisions to exist, though even the microscope 
cannot reveal to us their boundaries. 

506. It would lead me into too long a discussion to examine 
fully the evidence in regard to these pretensions of phrenology. 
Besides stating the general fact, that the failures in describing 
mental and moral character from external examinations of the 
head are such, when the examination is conducted fairly, as to 
exhibit the falsity of these pretensions, I will only allude to one 
or two particular facts, and dismiss the subject. In the phre¬ 
nological map of the cranium there are located some half a 
dozen organs along in the region of the eyebrows. Now, you 
will remember that the frontal sinus extends along in this lo¬ 
cality. This sinus varies very much in size in different individ¬ 
uals. It is obvious, therefore, that an external examination 
can give us no accurate idea of the quantity of brain in that 
locality. Take another point. Phrenologists have always in¬ 
sisted that there was the most positive evidence, from examina¬ 
tions of the head in man and in animals, that certain faculties 
or propensities have their organs in the locality where the 
cerebellum lies. But all this mass of vaunted evidence is swept 
away by the discovery stated in § 499, that the cerebellum is 
chiefly concerned in effecting the compound motions of the body. 
I might go on to examine in this way the rest of the evidence 
adduced in favor of the truth of phrenology, and show that 
there is no satisfactory evidence of the correct localization of any 
one of the organs paraded with such definiteness on the cranial 
map of this so called science. But it would occupy too much 
space. 

507. The only fact which seems to give any countenance to 
phrenology is that general fact, which is matter of common ob¬ 
servation, that the front and upper portion of the brain—that 
which occupies the forehead—is commonly developed in pro¬ 
portion to the development of the intellect. This would seem 
to show that the intellectual faculties have their seat in this 
part of the brain. But it is far from -proving this to be so. 
For it may be, that a general enlargement of the cerebrum is 
for some reason accommodated by having the forehead enlarged, 
in preference to other portions of the cranium. For it is evident 
that a brain which is larger alike in all its parts than usual, 
can, as it is a soft yielding organ, be equally well accommodated, 
whether the cranium be made of unusual size in only one direc- 




336 


HUMAN PHYSIOLOGY. 


Size of the front part of the brain. Facial angle. 


tion, or in all directions. The fact that in the child the forehead 
is more prominent than in the adult, is inconsistent with the 
supposition that the intellect has its seat especially in the front 
part of the brain, for the child has more of the instinctive and 
less of the intellectual than the adult. I may remark in this 
connection, that the phenomena presented by injuries and by 
disease in this part of the cerebrum, have not, as thus far ob¬ 
served, seemed to show that it is the peculiar seat of the intel¬ 
lectual faculties. 

508. The size of the anterior portion of the brain, above re¬ 
ferred to, may be estimated by the measurement of the facial 
angle , so termed, proposed by Camper, a Dutch naturalist. 
This angle is formed by drawing two lines as represented in 
Figures 185 and 186. The line, a, 6 , is drawn from the most 


FIG. 185. 


FIG. 186. 





C 


prominent part of the forehead to the front of the upper jaw. 
The line, c, rf, is intended to represent the line of the base of the 
brain, and runs from the orifice of the ear along on the floor of 
the cavity of the nose. It is manifest that the less prominent 
is the forehead, that is, the less brain there is in the front part 
of the head, the more acute will the angle be that is formed by 
these lines. In Fig 186, which represents the skull of a negro, 
this angle is more acute than in the skull of the European, Fig. 
185. In animals this facial angle is much more acute than in 
man. In the monkey tribe it varies from 65° to 30°, while in 
man its average is about 75°. The ancient Greeks, wishing to 
give the aspect of great intellectual superiority to their statues 
of deities and heroes, made it in them as high as 90°. 

509. It is proper to remark here, that while it is clear that, 
as a general rule, the amount of intelligence is to some extent 
proportioned to the amount of the cerebrum, both in man and 
in auimals, the rule is not an invariable one. Size is far from 







CONNECTION OF THE MIND AND THE BODY. 33T 

Mental difference between man and animals. Little difference in the brain. 

being the only measure of power in this case. What differ¬ 
ences there may be in intimate structure, to compare with the 
mental differences, we know not. Even where the rule stated 
above holds good, the difference in mere bulk is far from being 
proportionate to the mental difference. The mind of a Newton 
or a Shakspeare is gigantic compared with any common mind, 
but the brain in such cases is not very much larger than ordi¬ 
nary brains. 

510. In relation to the evidence drawn from a comparison 
between different animals, in regard to the functions of the 
nervous system, there is one significant fact which must not pass 
unnoticed. Though, as we rise in the scale of animal life in 
our observations, we find every new addition of functions coupled 
with some new additions of structure, until we come to the 
higher animals, we do not find this to be so when we pass from 
them to man. The brain, it is true, is larger in man than it is 
in them, and has much more of the gray substance ; but there 
are no essential differences of structure in his brain, to corres¬ 
pond with the added mental qualities which so decidedly dis¬ 
tinguish him from the brutes. These qualities constitute some¬ 
thing more than a difference of degree. It is a difference of 
kind. And, therefore, it is a great and a significant fact, that 
there is no corresponding difference of kind in the organization 
of the brain. 

511. The qualities to which I refer I have alluded to in the first 
part of this book (§ 40). They are possessed by every hu¬ 
man being to some extent, however debased he may be; 
and, on the other hand, they are never possessed by any of the 
inferior animals, however high their mental manifestations may 
be, and however much they may be improved by training. 
Though there be so wide a distance between such minds as 
Newton, and Milton, and Shakspeare, and the lowest representa¬ 
tive of our race, yet in him are contained the elements of the 
excellence to which they arrived. But no one dare assert this 
to be true of the very wisest of the inferior animals. 

512. The distinction between man and animals is a definite 
one. It is as definite as it would be if it were based upon differ¬ 
ence of organization. The barrier is fixed; and not a step over 
it has any animal advanced, with all the training which may 
have been expended upon him. No animal, however intimate 
has his intercourse been with man, has ever acquired man’s 
habit of abstract reasoning, or manifested any real knowledge 
of the difference between right and wrong. Prof. Guyot does 

29 







333 


HUMAN PHYSIOLOGY. 


Intimate connection of the mind and the body. 

not speak too strongly when he says, “I will even go farther 
than is ordinarily done, and I will say, that there is an impassa¬ 
ble chasm between the mineral and the plant, between the plant 
and the animal; an impassable chasm betiueen the animal and 
many Surely if the impassable chasm between minerals and 
vegetables, and that between vegetables and animals, are worthy 
of note when we take a comprehensive view of the material 
world, so also is that which is much more manifest as existing 
between animals and man. When, therefore, the comparative 
physiologist, in his examination of mental manifestations in con¬ 
nection with physical developments finds, as he comes to man, 
that in him are peculiar and distinctive mental manifestations 
with no corresponding physical developments, he should deem 
it to be an important fact in science, which should not be slurred 
over, or passed unnoticed, as is often the case. I shall allude 
to certain bearings of this fact in another part of this chapter. 

513. In looking at the facts presented in this chapter and 
in that upon the Nervous System, you must have been contin¬ 
ually struck with the intimacy of the union between the mind 
and the body. On this subject I thus remark in another work. 
“There are various figures used to illustrate this connection. 
The most common one is that in which the mind is spoken of 
as dwelling in the body as a habitation. In a certain sense 
this is true. This tabernacle of flesh, as the Bible aptly terms 
it, is in its present state a habitation, which the mind is to leave 
in a short time, to return to it, however, at length, rebuilt and 
refitted in a more glorious, an incorruptible form, to dwell in it 
then forever. But this illustration of the mysterious connec¬ 
tion of the mind with the body is but a partial one—it does 
not express the extent nor the intimacy of that connection. 
The mind is not a mere dweller put into this habitation. Its 
union with it is not thus loose and easily severed. It is bound 
to its every nerve and fibre, so that the least touch of the body 
at any point affects the mind. Instead of being put into the 
body, it has, being thus interlaced, as we may say, fibre with 
fibre, grown with its growth and strengthened with its strength. 
In the feebleness of infancy the mind is just as feeble as the 
body, and they both grow together up to the vigor and firmness 
of manhood, and both decline together in old age. So close is 
their union through all the stages of life, and so equally is each 
affected by the joys and sufferings of the other, that we might 
justly conclude that at death, when the tabernacle crumbles 
into dust, the mind falls with it never to rise again, had not a 






CONNECTION OF THE MIND AND THE BODY. 339 


Sources of evidence in regard to the nature of the connection. 

divine revelation told us that, indissoluble as this connection 
appears during life. Almighty power will dissever it, and release 
the soul from the thousand ties that bind it to its habitation, at 
the very moment of its destruction. Were it not for this assur¬ 
ance of our immortality, we could look forward in the uncertain 
future to nothing but blank, drear annihilation, as awaiting our 
minds, just as it does the minds of the brutes that perish. 

514. In our carefulness to avoid materialism, we are too apt 
to look upon the mind and the body as two separate and inde¬ 
pendent things. At death they do indeed become so, but who 
of us knows that they would, were it not for the fiat of the Al¬ 
mighty ? Who knows that there is not a necessity for the 
putting forth of his power in each individual case at the time 
of death, to prevent the mind of man from dying with his body, 
just as the mind of the brute does with his? The very preva¬ 
lent notion that the mind is essentially indestructible, and that 
it is put into the body as a separate thing, having the power 
of itself to leave the body whenever it dies, rests on no sub¬ 
stantial proof. That it is destined thus to leave the body is 
quite another tiling.”* 

515. The nature of the connection of the mind and the body 
is a great mystery. Still, there are many things which we can 
know in relation to it. The sources of our knowledge on this 
subject are three, viz., the investigations of Physiology , the tes ■ 
timony of Consciousness , and that of Revelation. Each of 
these kinds of evidence throws light upon the others. If, 
therefore, we use all of them, giving to each its due limits and 
force, we shall come to some certain and valuable conclusions. 
But if we take any one of them alone, we shall be liable to be 
led into gross error. 

516. There is in some physiologists a disposition to rely upon 
physiology alone, to the exclusion of the other sources of evi¬ 
dence, in "the investigation of this subject. In doing this they 
are driven to this alternative. Either they must be content 
with a very limited knowledge of the subject, or they must rely 
upon mere presumptive evidence for many of their conclusions. 
And commonly the latter is the course which they pursue. 
They are not content with the very limited conclusions to which 
thev are shut up by the absolute proof furnished by physiology. 
They boldly reason, therefore, upon what they deem to be 


* 1; Physician and Patient,” from the Chapter entitled “ The Mutual Influence ol 

the Mind and Body in Disease.” 







340 


HUMAN PHYSIOLOGY. 


Endowments of matter. Is intelligence one of them"? 

probable. And they are invariably led into error. This I pro¬ 
pose now to show. 

517. In order to get definite ideas of the manner in wnich 
the erroneous conclusions are arrived at, let us view matter in 
its various states and connections. Unorganized dead matter 
you see to be entirely different in some important respects from 
living organized matter. The distinction is a definite one. It 
is easily recognized, and none but dreamers in science have 
failed to see it. Though Robinet and others of his class have 
sought to obliterate it, in carrying out their fanciful notions, 
(§ 48,) and though some have supposed that there was a latent 
life in all unorganized matter, ready to be called into action on 
the application of the appropriate excitants, it is considered by 
all rational observers as a settled point, that there is an essential 
distinction between common dead matter and living matter. 
The latter is endowed with certain properties that the former 
has not. They are termed vital properties. They control to a 
certain extent the mechanical and chemical properties which 
both forms of matter have in common. Some suppose that 
what we call life is a single principle; but others suppose the 
endowment to be compound, made up of different principles or 
properties. But this question we need not discuss. All that 
concerns the view I am presenting is the mere fact of the en¬ 
dowment. 

518. Let us go a step farther. Some living beings have more 
endowments than others. All have those of organic life in 
common (§ 32). But there is an animal life also, which by 
means of the nervous system is superadded to the organic. 
And, as we trace the animal kingdom from the lowest animal 
up to man, we find the endowments connected with this system 
multiplied as we advance, till in him they are more complicated 
and extensive than in any other animal. This is especially true 
of intellectual endowments, those which are merely instinctive 
being more developed in many, perhaps we may say most, of 
the inferior animals. And in man we find special mental 
endowments, of which other animals present not the faintest 
trace. 

519. Now the question arises, whether intelligence is like 
life, a mere endowment of matter, or whether it is in some 
measure independent of it. In other words, whether it is a 
principle or set of principles with which matter is endowed, or 
an immaterial something which acts through matter as its in¬ 
strument. How much does bare physiology teach us on this 




CONNECTION OF THE MIND AND THE BODY. 3*1 


Reliance on evidence from physiology alone leads to materialism. 

question ? It has often been claimed that it can teach us much, 
and the most bold conclusions have sometimes been ventured 
from this quarter. But mere speculation has in all such cases 
been deemed to be proof. Physiology does show us, as I have 
before said, that the spiritual is in this world always connected 
with the material, and that mind never acts independently of 
the matter with which it is connected in the brain. But it 
gives us no light upon the nature of this connection. It is 
well for us to know how deficient are its teachings on this point. 
For all that it can teach us, we know not but that the mind 
may be a mere result of action in matter. It neither tells us 
that it is so, or that it is not. It leaves us entirely in the dark 
on this point. Indeed so far as it affords presumptive evidence, 
it appears to teach, that mental phenomena are results of mat¬ 
ter, acting in consequence of certain endowments or tendencies 
imparted to it, just as secretion is in living substances, or chem¬ 
ical action in those which are not living. Accordingly those 
who have relied upon physiology alone on this subject, have 
adopted various forms of materialism. Some have supposed 
that thought is a mere product of matter, and that the brain 
secretes it as the liver secretes bile. Others have taught that 
the mind is “a bundle of instincts,” each residing in some par¬ 
ticular part of the brain as its organ. This has been the doc¬ 
trine of some prominent phrenologists. 

520. Let us look at living matter in another point of view, 
and see to what physiology alone, if at all venturesome in draw¬ 
ing conclusions, will lead us. Let ns look at the origin and 
growth of the thinking animal. Take, for example, an animal 
the formation of which we traced in the Chapter on Cell-Life, 
§ 210. The b-ginning of the bird as it forms in the egg is a 
simple cell filled with a fluid. This produces other cells, and 
soon the organs and the limbs of the animal are formed. At 
length the animal bursts the shell, and comes out not only a 
living and sentient being, but a thinking being. It has a mind 
which feels desires and emotions, and prompts the muscles to 
action to effect its purposes. Organization here precedes the 
development of mind so far as we can see, and therefore it would 
seem that mind is a result of organization. Especially does 
this appear to be so, when we find that the amount of mind in 
different animals is proportioned to the amount of a certain part 
of the organization, the brain. All this is as true of man as it 
is of other animals. And besides, we see in man that as the 
organization becomes perfected, the intelligence is proportiona- 




342 


HUMAN PHYSIOLOGY. 


Action of formative vessels like instinct, and even intelligence. 


bly increased. In infancy, when the organization of the brain 
is imperfect, the intelligence is small in amount, and grows with 
the growth, and strengthens with the strength of the brain. 

O' C* o % 

And as the mind thus grows with the body, it appears to perish 
with the dissolution of the organization, and in the case of the 
inferior animals undoubtedly does so. 

521. But it may be said, that the physiologist observes that 
the mind designs, and devises means to carry out its designs, and 
this shows that there is an immaterial principle that moves the 
machinery of the material organization. This is a plausible 
view of the subject, but it is only plausible. Physiology alone 
cannot prove it to be a correct view. For, if we limit ourselves 
to her teachings alone, it can be made to appear by the same 
line of argument, that mind is at work in all the phenomena 
that we see in living beings. In the formation of any part, as 
you saw in § 163, in the Chapter on Formation and Repair, 
the formative vessels work after a fixed plan, and cooperate to¬ 
gether to accomplish the object. They seem to act intelligently, 
as if they had a mind by which they designed, and devised 
means for carrying out their designs. And the formative and 
other vessels thus act together, proportioning means accurately 
to ends, not only under fixed and regular circumstances, but they 
do so under varying circumstances, to meet exigencies. Thus, 
when an artery supplying a limb is tied, § 169, the formative ves¬ 
sels enlarge the arteries in the neighborhood, in order that the 
blood may be supplied to the limb in suitable quantity. That is, 
they construct after a larger pattern to meet the new want, just 
as if they were informed of it and acted accordingly. Take 
another example afforded by the formation and discharge of an 
abscess, as described in § 170. In this case, as the abscess 
forms, various operations are going on, with different sets of 
vessels cooperating together to effect a common purpose. And 
when the abscess has made its way to the surface, and dis¬ 
charged itself at an outlet, a change comes over the operations, 
in order to restore the part to its usual state. The different 
vessels accommodate themselves to this change, as if they were 
intelligent workmen, acting in conformity to a design or plan 
of their own, upon which they had agreed. Other examples 
might be cited, both from vegetable and animal life, all showing 
design and cooperation in effecting purposes. 

522. In such phenomena we see a striking analogy to those 
of instinct, and even to those of intelligence also. It is this 
analogy which has led some in their speculations to adopt the 




CONNECTION OF THE MIND AND THE BODY. 348 

Conflicting evidence of Physiology. 


idea that life and soul are the same thing. Hence, too, many 
phenomena in vegetable life are in common language often 
called instinctive. Thus, it is said, that when a seed sprouts, 
the roots instinctively seek the ground, and the stalk and branches 
instinctively seek the air and the light. This is even the case 
sometimes when the seed is placed at some little distance from 
the ground. So, too, if a plant that naturally grows in we't 
ground is put into dry soil, but in the neighborhood of a wet 
spot, it shoots forth roots abundautly towards this spot, rather 
than on the other side. 

523 . But the evidence from physiology does not all tend to 
materialism. There is some negative evidence which has a 
different bearing. I refer to the fact stated in § 510 , viz., that, 
white man differs in his spiritual nature so widely and so spe¬ 
cifically from the inferior animals, his brain exhibits no corres¬ 
ponding specific difference in structure, but only a difference in 
amount. The difference in degrees of intelligence in the animals 
below man is marked by a corresponding difference in the 
amounts of the gray substance. And if it were true that man, 
as some think, differed from them only in having a higher de¬ 
gree of intelligence, we should expect to find in him a mere 
increase cf this substance. But as his mind differs from theirs 
not merely in degree, but in kind also, we should have reason 
to expect, if mind were wholly dependent on organization, that 
the anatomist would find not only an increase in the quantity 
of the gray substance, but also a difference in its structure. 

524 . But strong as this evidence is, it appears to be strongly 
rebutted, perhaps almost overborne, by the other evidence which 
X have cited from physiology. And the physiologist might 
perhaps say that, although as yet no difference of structure has 
been found that corresponds with the mental difference, future 
investigations with the microscope may discover some subtle 
difference of structure which now escapes our notice. But this 
it must be allowed is. not at all probable. On the whole it may 
be remarked, that the fact of which I have been speaking, although 
significant and valuable as being coincident with evidence drawn 
from the other sources, yet considered simply in connection with 
the physiological evidence, the evidence from the other sources 
being wholly shut out, it is doubtful how much weight it ought 
to have. The physiological evidence, taken by itself is con¬ 
flicting, and looking at the whole scope of it, the preponderance 
must be acknowledged to be towards materialism. 

525 . It is quite clear then, that the physiologist cannot well 




344 


HUMAN PHYSIOLOGY. 

Physiologist needs other evidence. Consciousness. 


avoid materialism, if, in examining the connection between the 
mind and the body, he rejects all evidence beside that which 
physiology furnishes. PIe can be saved from this result only by 
being content with the narrow limits, to which he is shut up, if 
he confine himself to absolute proof. As we have already seen, 
the positive knowledge that physiology gives us on this subject 
is exceedingly narrow. We soon come to the line that divides 
between the known and the supposed. And if we attempt to 
go beyond that, our conclusions as to what is probable will 
quite certainly lead us to the result which I have pointed out. 
The need, therefore, of the evidence drawn from the other 
sources that I have mentioned is most palpable. The physiol¬ 
ogist must confess himself to be under the necessity of going 
out of his physiology, in order to learn all that can be learned 
upon this subject. At the best, there is much mystery in rela¬ 
tion to it which we cannot penetrate, with all the light that we 
can bring to bear upon it. And the mystery is deep indeed, 
when we call to our aid only the dim light of physiology. It 
needs some other light to deliver us from the confusion of ideas, 
into which we are introduced by the analogy existing between 
the phenomena of life and instinct and intelligence, in relation 
to their connection with the organization of matter. Let us 
look then at the evidence which comes from the other two 
sources, viz., our consciousness, and revelation. 

526. Every individual is conscious that, as he feels and thinks 
and acts, he, that is his mind or spirit, acts upon the structure 
of his body, and is acted upon by it. It is not a consciousness 
that he as a material body does all this. He feels that it is a 
power within that does it, and he instinctively separates in his 
ideas the power from the different parts of the body, and from 
the body as a whole. He is conscious too of a responsibility in 
relation to the thoughts and acts of the spirit within. He has 
a knowledge of right and wrong, and has self-reproach on doing 
wrong, and self-approbation on doing right. It is this conscious¬ 
ness of a self-acting immaterial spirit in this material body, that 
constitutes the basis of all character, and of all the moral rela¬ 
tions of man to his fellow man, and to his Maker. Every body 
acts upon the testimony of this consciousness as being valid and 
certain testimony. And, however the physiologist may reason 
about matter and mind, as if the latter were a mere product or 
endowment of the former, yet as a man, as a member of society, 
as a subject of government and law, he cannot avoid acting 
upon the ground, that mind in a certain sense controls matter, 





CONNECTION OF THE MIND AND THE BODY. 34S 


Evidence from consciousness confirmed by Revelation. 


and is responsible for its acts independently of the matter with 
which it is connected. 

527. Now the evidence which this consciousness affords us 
should suffice to keep us from the materialism, into which phvs- 
iology taken alone would be apt to lead us. It shows us that, 
although the mind is developed with the material organization, 
and can act only with it, it is not its mere product, nor one of 
its endowments. It shows us, on the other hand, that it is in 
some measure independent of matter, and that its dependence 
upon it is only a dependence of connection, matter being the 
instrument of mind, through which it acts on external things, 
and is acted upon by them. The evidence from this source is 
of a positive character. We are driven by it to the alternative, 
of believing that the mind is an immaterial, self-acting agent, 
in some measure independent of matter, or of harboring the 
impious and monstrous belief, that the Creator has implanted 
in the bosom of man a lie, and that he is living a horrible farce, 
acting in view of moral relations and responsibilities that have 
no existence. 

528. This positive testimony of our consciousness is confirmed 
by the testimony of revelation. This is not done by any formal 
array of proof. The existence of the spiritual part of man as 
a seif-acting responsible agent is assumed as a fact that needs 
no proof. All the statements, and teachings, and appeals of the 
Bible recognize it as a fact known to the consciousness of every 
man. The Bible, therefore, may be considered as simply affirm¬ 
ing that the testimony of our consciousness on this point is 
valid testimony. But the Bible goes farther than this. It 
gives us one great fact of which neither physiology nor our con¬ 
sciousness could assure us. I refer to the mind’s immortality. 
Our consciousness could, it is true, give us presumptive evidence 
to show that the soul with its high powers and aspirations is to 
live after the death of the body. But it could furnish us no 
absolute proof of the fact. And its presumptive evidence would 
be effectually rebutted by the presumptive evidence from physi¬ 
ology, which, as you have seen, points in another direction. 
We are so familiar with the mind’s immortality as a known fact, 
and we so uniformly think of it in connection with the death 
of the body, that we are not aware how absolutely dependent 
we are upon revelation for all that we know in relation to it. 
If there were no revelation, and death were to us an unknown 
event, and we were now for the first time called upon to witness 
the death of a friend, how little should we know, and how con* 




346 


HUMAN PHYSIOLOGY. 


Immortality revealed only by revelation. 

fused would be our thoughts in relation to the great mystery 
before us! “ What is it ? ” we should ask. “ Is it sleep ? v 

No. We never saw any one sleep thus. What is it ? Who 
can tell us?” And we should wonderingly watch to see some 
signs of awakening, not giving up all hope till decay begins its 
ravages on the loved form before us. Then, as we should from 
the dictate of nature, consign to the earth the friend who was 
so recently among us a breathing, moving, speaking man, now 
a mere mass of decaying matter, we should feel that we bury 
there not the body only, but all that belonged to that body 
during life—the whole man. Thought and feeling, as well as 
life and motion, would appear to us, untaught of God, to be 
extinguished in the grave. Even if some one should utter all 
tremblingly the hope, that there might be a subtle spiritual 
part of our friend, that would some time in some form return 
again to our society, that hope would at once be crushed by 
the reflection that whatever it was in our friend that thought 
and felt, it came into existence with the body, was infantile 
when the body was, grew with the growth of the body, and 
strengthened with its strength, and therefore now, so far as we 
can see, has perished with it. Nature utters no voice to tell us 
otherwise. She emits no light to illumine the grave. Dark¬ 
ness and silence rest there, till the light of revelation shines 
upon it, and God proclaims man’s immortality. 

529. I have thus spoken of the three sources of evidence in 
regard to the connection of the mind and the body, and have 
indicated the character of the evidence furnished by each. I 
have shown particularly that if the attention be confined to that 
which is furnished by physiology, the mind is apt to be led into 
materialism. But the attention should not thus be confined. 
All the three kinds of evidence should be employed and should 
be brought to bear upon each other. If this be done, the dis¬ 
crepancies in the evidence from physiology are cleared up by 
the evidence afforded by consciousness and revelation, and we 
see the true value and bearing of the fact, that the specific men¬ 
tal difference between man and animals is not attended with a 
corresponding structural difference. Though this fact operates 
merely as conflicting evidence, when taken simply in connection 
with the. rest of the facts developed by physiology; when, we 
come on the other hand, to take the whole range of evidence 
from the three sources spoken of, it is exceedingly satisfactory as 
concurring with the testimony of consciousness and revelation. 
A.t the same time, those physiological phenomena, which taken 




MAN AND THE INFERIOR ANIMALS. 


347 


Evidence from consciousness and Revelation positive. 


--- \ 

by themselves seem to show so strongly that the mind is wholly 
dependent upon organization, are so interpreted by the evidence 
from the other sources, that the dependence is seen to be for 
the most part a dependence of connection only, the brain being 
the instrument of the mind. 

530. The evidence from consciousness and revelation is of the 
most positive character, and cannot be set aside by evidence 
from any other source. Other evidence may serve to interpret 
it, but cannot nullify it. The attempt is sometimes made to set 
it aside by urging the presumptive evidence of physiology, as 
if it were absolute proof. But most physiologists engage in no 
such futile and unchristian efforts, but give due weight to the 
testimony of consciousness and revelation in all their investiga¬ 
tions of the mysterious connection of the mind and the body. 
The influence of Carpenter, an English physiologist, whose works 
are more extensively used by students than those of any other 
physiologist, is especially to be commended in this respect. And 
although skepticism occasionally utters its plausible falsities, de¬ 
ceiving the superficial and the speculative, we have no fears 
from present indications that the votaries of physiological science 
will, as a body, be arrayed in opposition to Christianity. 


CHAPTER XVIII. 

DIFFERENCES BETWEEN MAN AND THE INFERIOR ANIMALS. 

531. I have already treated somewhat of the differences be¬ 
tween man and the inferior animals in different parts of this 
oook, and especially in the preceding chapter. But it has been 
done only incidentally, and the subject demands at our hands a 
more thorough and systematic investigation. This I propose to 
do in the present chapter. 

532. Lord Monboddo maintained that man is only an im¬ 
provement on the monkey, occurring as a result from the general 
tendency to advancement claimed to exist in nature. He seemed 
to think that man bore a relation to the monkey somewhat like 





348 


HUMAN PHYSIOLOGY. 


Lord Monboddo. Nature of instinct a mystery. 

that which the frog bears to the tadpole, as described in § 167, 
and that as the tadpole becomes the frog, so the race of man 
was produced by a change at some remote period of the crea¬ 
tion, of the monkey into a man. This ridiculous notion of the 
erudite but fanciful Scotch philosopher is really but another 
phase of the more recent theory of gradation, or development, 
as it is sometimes called, which in different forms is now advo¬ 
cated by so many European philosophers. And, although few, 
comparatively, adopt this theory definitely and fully, there is 
quite a disposition among many to obliterate the distinctions by 
which the Creator has in so marked a manner separated man 
from the inferior animals. It is well, therefore, that we should 
have a clear idea of these distinctions. 

533. It is often very loosely said that while man is governed 
by reason, instinct rules in the animal.* If it be meant by this 
that, as a general rule, reason predominates in man, while in¬ 
stinct does so in animals, the statement is a correct one. But 
if it be meant that animals are wholly governed by instinct, and 
that man is distinguished from them as a reasoning animal, it 
is not correct. For some animals do reason, that is, if making 
inferences be considered as reasoning. In tracing out the differ¬ 
ences between man and animals I shall not attempt to show 
what the nature of instinct is. This is a great mystery, and all 
attempts to solve it have utterly failed. I shall content myself, 
therefore, with pointing out some of the differences between in 
stinct and reason. In doing this it is not always easy to say 
just where the one begins and the other ends, so intimately are 
their phenomena often mingled together. 

534. The actions of instinct are more unaccountable than 
those of reason. In the operations of reason we see something 
of the processes by which results are reached. But it is not 
so with instinct. For example, as a man travels over an unex¬ 
plored country, we can understand by what means he obtains a 
knowledge of the country, in order to guide him on his journey. 
The processes of his reasoning in regard to this we can com¬ 
prehend. But when an insect travels with unerring certainty 
to its place of destination without any guide marks that we can 


* Some explanation may be well here in relation to the different uses made of the word 
animal in different connections. Here it is used in contra distinction to rmn. So it is 
used in the expression, man and nnimnls. But ns man is in certain senses an animal, 
whenever we wish to recognize this fact we speak of other animals as the inferior ani¬ 
mals. And thus in regard to animals, we speak of their higher and lower orders, lha 
higher of course being those that approximate nearest to man. 





MAN AND THE INFERIOR ANIMALS. 


849 


Instinct governed by invariable rules. Mysterious in its operations. 

see,* or when a swarm of bees or a flock of birds wing* their flight 
to distant places, or when bees construct their honey-comb with 
the exactness of mathematics in obedience to the best principles 
for such a structure, we cannot understand the processes which 
lead to the result. It seems to be produced by an impulse from 
a cause extraneous to the animal, guiding it as if it were a mere 
machine. The little intelligence of the animal seems to have 
only an incidental connection with this impulse. It, therefore, 
merely controls somewhat the circumstances under which the 
instinct acts. 

535. So little has the intelligence to do with the instinct, and 
so nearly mechanical therefore are the actions of the latter, that 
they are governed by an invariable rule. It is as invariable 
almost as are the movements of a machine. For this reason 
there are no improvements or alterations in the acts of instinct. 
The bird and the bee, for instance, have no change of fashion 
in their architecture from age to age. The honey that fed 
John the Baptist, or that which was found by Samson in the 
carcase of the lion, was deposited in the same hexagonal cells 


* I will introduce here ns an illustration, a little incident recorded in my note book 
many years ago. The account of it runs thus: I was much entertained to-day in watch¬ 
ing the movements of n very small winged insect—about one-third of the size of a com¬ 
mon fly. He was dragging a dead spider across the road. Every now and then he would 
drop his load, and run forward a little, springing about here and there, and then would 
go back and take up his load again. His movements in this way were so quick and ap¬ 
parently so irregular, that they seemed to be without an object. But I observed, that 
although he thus ran about here and there, his course in its general bearing was a very 
straight one. Soon a waggon passed along directly over where the insect was, separating 
him from his load, and disturbing the whole surface of the ground. He, however, soon 
found his load, and then with a good deal of apparent reconnoiter ng he went on again in the- 
mine general course. In the latter part of his journey he travelled over and nmidst a heap 
o f stones. Here he would occasionally leave the spider and disappear, and then return 
again to take his load. Again a little farther on I would see him emerge from his con¬ 
cealed pathway, and so on to the end of his journey. His place of destination was a hole 
in the sand beneath a flat stone. Now, how did this insect in his journey to his home, 
(which to him was a long one, though only three rods,) manage to keep so straight a 
course? Was it in the same way that men manage in their journeys, guided by way- 
marks, and by information obtained from others ? Following out this idea, suppose then 
a man to be at the same distance from his home in proportion to his size that the insect 
was from his home. According to this supposition he must be over three thousand miles 
from home. Suppose the direct line to his home Iny across an uninhabited country, so 
that he can get no information from others. This makes his case parallel with the in¬ 
sect's, for we saw him meet no other insects on the road. Now, if he knew the exact 
direction in which his home lay. he could not, without his compass, move with any pre¬ 
cision towards it. And if he had wandered away from it without a compass, ns the in¬ 
sect did from his home, how would he know in what direction it lay ? And yet the insect 
travelled towards his home as if he preserved exactly amid all his wanderings the points 
of the compass. The surface over which he went was very irregular. He had to cross 
or wind around eminences, which were to him as large ns hills and mountains are to man, 
and yet he was not embarrassed; and when he went among the stones he had more and 
greater difficulties to encounter than man meets with in passing through the wildest coun¬ 
tries. Again, suppose that, the travelling man should meet with some whirlwind or some 
convulsion of nature, which should separate him from his burden, and disarrange in some 
measure the face of the country about him. just as the travelling insect was served by the 
commotion of the horse’s feet and the wheels of the waggon. Would he find his load as 
easily as the insect did, and go on his way with as little hesitation? 

30 







850 


HUMAN PHYSIOLOGY. 


Contrivances in the nests of birds. 


which are constructed by the bees of the present day. And 
each bird builds its nest precisely in the same way that its an- 


FIG. 187. 



NEST OF THE BAYA. 


cestral birds have ever done. Most birds’ 
nests are constructed after the same general 
pattern. But sometimes we observe strik¬ 
ing peculiarities to subserve some special 
purpose. Fig. 187 represents the nest of 
the Bay a, a little bird of Ilindoostan. It 
is in the shape of a bottle, and is made of 
long grass. It is suspended from a slen¬ 
der branch of a tree, so that monkeys, 
serpents, &c., cannot reach it. The en¬ 
trance to the nest is made on the under 
side, so that these animals cannot enter, 
while the bird itself can readily fly in. It 
is divided into apartments, in one of which 
the female sits upon the eggs, while in the 
other the male bird “ solaces his companion 
with his song whilst she is occupied in ma¬ 
ternal cares.” In Fig. 188 is seen the nest 
of another little eastern bird, which with 
filaments of cotton taken from the cotton 
plant, sews leaves together with its beak 
and feet, so as to conceal the inclosed nest 
from its enemies. 


FIG. 188. 



NEST 

of the Tailor Bird. 






MAN AND THE INFERIOR ANIMALS. 


851 


Contrivances in the honey-comb. Mathematical principles exactly applied. 

536. While there is no change in the acts of instinct they 
are marked by perfection. That is, they are perfectly adapted 
to the purposes to be effected and to the circumstances under 
which they are performed. The Creator, who directs the im¬ 
pulse that governs the animal, in this case as well as in all 
others, accurately fits the means to the ends to be accomplished. 
There is nothing in which this perfection of instinct is better 
shown than in the construction of the honey-comb. The cells 
are made hexagonal, because in this way all the space is occu¬ 
pied—there is no waste of room. If the cells were made cir¬ 
cular, there would not only be a waste of room, but a large 
quantity of material would be needed to fill up the spaces be¬ 
tween the cells. The difference can be seen in the two Figures 
189 and 190. Each comb, it is to be observed farther, has two 

FIG. 189. FIG. 190 




sets of cells, the ends of one set being arranged against the ends 
of the other in a peculiar manner. These ends are not flat, but 
each one has three plane surfaces, forming with each other a 
particular angle soon to be noticed, and uniting together at the 
centre in a point. In the arrangement of these cells, therefore, 
a cell of one set does not lie end to end with a cell of another 
set. Its three surfaces form a part of 
the bottom or end of three cells of FIG - 19L 

the other set. This is made clear by 
Fig. 191, in which a cell of one set is 
represented as it abuts against a cell 
of the other set by one of its surfaces, 
its other two surfaces forming a third 
part of the ends of two other cells. Now it has been found 
that the angle formed at the edge of these surfaces between the 
two sets of "cells is such as to secure the greatest strength with 
the least amount of material. It was at one time thought that 











352 


HUMAN PHYSIOLOGY. 


Wonderful operations of instinct in communities among animals. 


this was proved to be not exactly true. The variation from the 
correct angle, made out by the calculations of the mathemati¬ 
cians, was indeed a slight one, but still it was variation enough 
to show, if the calculations were correct, that the workings of 
instinct were not perfect in this case. But the investigations 
of Lord Brougham have satisfactorily shown that the mathe¬ 
maticians were wrong in their calculations, and that the bees 
are right. 

537. The perfection of the operations of instinct is shown in 
the most wonderful manner in the regulation of communities of 
animals. Here we see cooperation to produce results effected 
through an irrational, and therefore in some measure a blind 
instinct. This social instinct is most extensively exemplified 
among the insect tribes, as for instance the bee and the wasp. 
The structures, resulting from the cooperation of multitudes of 
little laborers guided by this instinct, are very interesting. I 
shall allude to but, a single familiar example, the construction 
of the nests of wasps. These insects make their building ma¬ 
terial from the fibres of old wood. These they convert by mas¬ 
tication into a pulp, which made into a thin layer, becomes firm 
like paper. It is indeed a process very much like the common 
process of paper-making invented by man, and the first rude, 
inventor may have got his idea from the insect. With this 
substance the wasps build several ranges of cells, which are 
hexagonal, like the cells in the comb of the bee. These ranges 
of ceils are placed parallel to each other, at regular distances, 
with little supporting columns between them, as seen in Fig. 
192, 

The number and variety of instincts of the ordinary hive bees 
are very wonderful, but it would occupy too much space to de¬ 
scribe them. 

538. The wonderful cooperation of animals in obedience to 
social instinct, in the building of habitations and other struc¬ 
tures is seen in several of the mammalia. But it is most won¬ 
derful in the beaver, the following description of whose habits 
in this respect I take from Carpenter. “ During the summer it 
lives solitarily in burrows, which it excavates for itself on the 
borders of lakes and streams; but as the cold season approaches 
it quits its retreat and unites itself with its fellows, to construct, 
in common with them, a winter residence. It is only in the 
most solitary places that their architectural instinct fully devel¬ 
ops itself. Having associated in troops of from two to three 
hundred each, they choose a lake or river, which is deep enough 




MAN AND THE INFEKIOR ANIMALS. 


353 


Exemplified in the beaver community. 


FIG..192. 



NEST OF WASPS. 


to prevent its being frozen to the bottom; and they generally 
prefer running streams, for the sake of the convenience which 
these afford in the transportation of the materials of their erec¬ 
tion. In order that the water may be kept lip to a uniform 
height, they begin by constructing a sloping dam ; which they 
form of branches interlaced one with another, the intervals be 
tween them being filled up with stones and mud, with which 
materials they give a coat of rough-cast to the exterior also 
When the dam passes across a running stream, they make if 
convex towards the current; by which it is caused to posses? 
much greater strength than if it were straight. This dam i? 
usually eleven or twelve feet across at its base, and is enlarged 
every year; and it frequently becomes covered with vegetation 
so as to form a kind of hedge. 

589. When the dam is completed, the community separate* 

SO* 







854 


HUMAN [PHYSIOLOGY. 


Blindness of instinct exemplified. 


into a certain number of families; and the beavers then employ 
themselves in constructing huts, or in repairing those of a pre¬ 
ceding year. These cabins are built on the margin of the Avater; 
they have usually an oval form, and an internal diameter of six 
or seven feet. Their walls are constructed, like the dam, of 
branches of trees; and they are covered, on two of their sides, 
with a coating of mud. Each has two chambers, one above the 
other, separated by a floor; the upper one serves as the habita¬ 
tion of the beavers, and the lower one as the magazine for the 
store of bark, which they lay up for their provision. These 
chambers have no other opening, than one by which they pass 
out into the water. It has been said that the flat oval tail of 
the beavers serves them as a trowel, and is used by them in 
laying on the mud of which their erections are partly composed; 
but it does not appear that they use any other implements than 
their incisor teeth and fore-feet. With their strong incisors they 
cut down the branches, and even the trunks of trees which may 
be suitable; and by the aid of their mouths and fore-feet, they 
drag these from one place to another. When they establish 
themselves on the bank of a running stream, they cut down 
trees above the point where they intend to construct their dwell¬ 
ings, set them afloat, and, profiting by the current, direct them 
to the required spot. It is also with their feet that they dig up 
the earth they require for mortar, from the banks or from the 
bottom of the water. These operations are executed with ex¬ 
traordinary rapidity, although they are only carried on during 
the night. When the neighborhood of man prevents the 
beavers from multiplying to the degree necessary to form such 
associations, and from possessing the tranquillity which they 
require for the construction of the works just described, they 
no longer build huts, but live in excavations in the banks of the 
water.” 

540. Instinct moves straight on to its result, and it does so 
blindly. It exercises no intelligence in regard to the purpose 
for which the result is intended, or the circumstances which 
tend to defeat this purpose. It evidently in some cases never 
knows any thing of the purpose aimed at by its acts, as, for ex¬ 
ample, when an animal makes provisions for a progeny which 
it is never to see. “ It is scarcely possible,” says Carpenter, 
“to point to any actions better fitted to give an idea of the na¬ 
ture of instinct, than those which are performed by various 
insects, when they deposit their eggs. These animals will never 
behold their progeny; and cannot acquire any notion from ex- 




MAN AND THE INFERIOR ANIMALS. 


355 


Results of instinct mingled with those of reason. 

perience, therefore, of that which their eggs will produce; never¬ 
theless they have the remarkable habit of placing, in the neigh¬ 
borhood of each of these bodies, a supply of aliment fitted for 
the nourishment of the larva that is to proceed from it; and 
this they do, even when they are themselves living on food of 
an entirely different nature, such as would not be adapted for 
the larva. They cannot be guided in such actions by any thing 
like reason; for the data on which alone they could reason 
correctly, are wanting to them; so that they would be led to 
conclusions altogether erroneous if they were not prompted 
by an unerring instinct , to adopt the means best adapted for 
the attainment of the required end.” 

541. The results of reason are often mingled with those of 
instinct in such a way that it is difficult to distinguish them 
from each other. But instinct is of itself wholly irrational. 
If it were not so, it would avoid acting whenever action would 
evidently be useless. But instinct has not the eyes of reason 
to see when this is the case. It leads the animal blindly on; 
so that, although under all ordinary circumstances the object 
is accomplished definitely and in the best manner, yet there is 
no capability of making provision for extraordinary circum¬ 
stances. Therefore, actions are occasionally performed, which 
do not at all answer the purpose which the instinct is designed 
to effect. Instinct, though perfect in its action under the fixed 
uniform circumstances under which it is destined to act, is a 
kind of blunderer when irregular circumstances arise. Instinct 
is a strict routinist, while reason readily accommodates itself 
to endlessly varying circumstances. In illustration of the 
above characteristic of instinct, I will cite a few examples. 
The hen will sit on pieces of chalk shaped like eggs, as readily 
as she will on the eggs themselves. Her instinct is so blind 
as to be deceived by this general resemblance. The flesh-fly 
often lays its eggs in the carrion-flower, the odor of which is 
so much like that of tainted meat as to deceive the insect. 
An amusing illustration of the blind disregard of circum¬ 
stances in following out the promptings of instinct is given by 
a gentleman, Mr. Broderip, in an account of a beaver Avhich 
he°caught when very young. As soon as it was let out of its 
cage, and materials were placed in its way, it began to build 
after the fashion followed by these animals when they construct 
their dam in a stream of water and build their habitations in its 
banks. “Even when it was only half grown,” says Mr. B., “it 
would drag along a large sweeping-brush, or a warming-pan, 








356 


HUMAN PHYSIOLOGY. 


Blindness of instinct illustrated in the beaver. 


grasping the handle with its teeth, so that the load came over 
its shoulder; and would endeavor to lay this with other ma¬ 
terials, in the mode employed by the beaver when in a state 
of nature. The long and large materials were taken first; 
and two of the largest were generally laid cross-wise, with one 
of the ends of each touching the wall, and the other ends pro¬ 
jecting out into the room. The area formed by the cross¬ 
brushes and the wall, he would fill up with hand-brushes, rush- 
baskets, books, boots, sticks, cloths, dried turf, or any thing port¬ 
able. As the work grew high, he supported himself on his tail, 
which propped him up admirably; and he would often, after lay¬ 
ing on one of his building materials, sit up over against it, ap¬ 
pearing to consider his work, or as the country people say, ‘judge 
it.’ This pause was sometimes followed by changing the position 
of the material judged; and sometimes it was left in its place. 
After he had piled up his materials in one part of the room, 
(for he generally chose the same place,) he proceeded to wall 
up the space between the feet of a chest of drawers which stood 
at a little distance from it, high enough on its legs to make 
the bottom a roof for him; using for this purpose dried turf 
and sticks, which he laid very even, and filling up the interstices 
with bits of coal, hay, cloth, or any thing he could pick up. 
This last place he seemed to appropriate for his dwelling; the 
former work seemed to be intended for a dam. When he had 
walled up the space between the feet of the chest of drawers, 
he proceeded to carry in sticks, cloths, hay, cotton, &c., and to 
make a nest; and when he had done, he would sit up under 
the drawers, and comb himself with the nails of his hind feet.” 
I simply remark in relation to this amusing narration, that you 
can see at once that if the instinct of this animal had been at 
all rational, it would not have impelled him to construct a dam 
and a dwelling in a common room, where they would be of 
no use to him. Reason would have dictated the building of 
a nest and nothing more. 

542. The care which animals exercise in relation to their 
progeny seems to be governed to a great extent, perhaps wholly, 
by a blind instinct. All care is given up when care is no longer 
needed, and with it what appears to be affection is given up 
also. In animals there is no such lasting affection of the pa¬ 
rent for the progeny as there is in man; for in them it is 
merely instinctive, and not rational and moral in its character, 
and it, therefore, lasts only so long as it is needed to carry out 
the purposes for which this particular instinct is designed. 




MAN AND THE INFERIOR ANIMALS. 


357 


Difference between the intelligence of man and that of animals. 


Indeed, in some cases there can be no affection in all the care 
which is instinctively exercised by the parent, for it is put forth 
for progeny which, as stated in § 540, the animal is destined 
never to see. And in those cases among* animals in which the 
family state exists, it is a mere temporary affair, and as soon 
as the offspring is able to take care of itself it is no more to 
the parent than any other animal of the same tribe is. 

543. But some animals have intelligence as well as instinct. 
"When this intelligence is shown in the mere power of imita 
tion it is of a low order. The parrot that learns to imitate 
man in speech is nothing like as intelligent as some animals 
that have no such power. Some animals have really a reason¬ 
ing intelligence—that is, they make rational inferences. Their 
reasoning is sometimes, as before remarked, so mingled with 
the operations of instinct, that it is difficult to distinguish them 
accurately. In the case of the beaver related in § 541, who 
labored so faithfully in obedience to a blind instinct, there was 
some exercise of reason, as, for example, when he “judged ” 
his work. But it is difficult to point out definitely the line 
between instinct and reason in such a case. There are some 
animals, however, in whom the workings of a reasoning intel¬ 
ligence are to be seen with perfect distinctness. But their 
reasoning differs from that of man. The inferences which the 
reasoning animal makes are individual; while man goes be¬ 
yond this, and makes general inferences, and therefore dis¬ 
covers general truths. Newton’s dog, Diamond, saw apples 
fall to the ground, as well as his master. And he was capable 
of making some inferences in regard to them; but they were 
individual inferences. For example, if an apple-tree were 
shaken, and the dog^were hit by a falling apple, whenever he 
saw other apples falling he would infer that he might be hit 
ao*ain, and would infer also that it was best for him to get out 
of harm’s way. This would be the extent of his reasonings. 
But his master inquired into the cause of the fall of the apple, 
and by considering this and other similar phenomena, he de¬ 
duced general principles, which govern the movements both 
of the atoms, and the worlds of the universe. 

544. The inferences which are formed by animals are mere 
results of the association of ideas, and the process, therefore, 
really hardly merits the appellation of reasoning. Thus, in 
the case of Newton’s dog, supposed above, the idea of the fa.ll- 
ino* apples was associated in his mind with the hurt experienced 
when he was hit, and prompted the getting out of harm’s way. 




358 


HUMAN PHYSIOLOGY. 


Reasoning in animals mere mental association. Exemplified. 


When such associations are extended and complicated, it ap- 
pears at first thought as if the animal acted in view of general 
truths, arrived at by the same process of reasoning that man 
employs. But it is a mere extension of mental associations. 
Thus, Newton’s dog probably associated the idea of being hit 
and hurt with other falling bodies beside apples. And so, too . 
various circumstances might come to be associated with the 
falling of bodies, and thus complicate the mental process which 
occurred when he saw any object falling near him. 

545. To show somewhat the extent to which this mental 
association operates in the brute mind, I will allude to some 
examples. A wren built its nest in a slate quarry, where it 
was liable to great disturbance from the blastings. It soon, 
however, learned to quit its nest, and fly off to a little distance, 
whenever the bell rang to warn the workmen previous to a 
blast. As this was noticed, the bell was sometimes rung when 
there was to be no blast, for the sake of the amusement in 
seeing the poor bird fly away when there was no need of alarm. 
At length, however, it ceased to be deceived in this way, and 
when it heard the bell ring it looked out to see if the workmen 
started, and if they did then it woi^ld leave its nest. In this 
case the bird merely learned to connect in its mental associa¬ 
tions two circumstances with the blasting, instead of the one 
from which it at first took the warning. The operation of 
this mental association is shown in a little different manner in 
the following case. Some horses in a field were supplied with 
water in a trough which was occasionally filled from a pump. 
As the supply was not always sufficient, one of the horses, more 
sagacious than the rest, whenever he, on going to drink, found 
the trough empty, pumped the water into it by taking hold of 
the pump-handle with his teeth, and moving his head up and 
down. The other horses seeing this, would, whenever they 
came to the trough and found it empty, tease the one that 
knew how to pump, by biting and kicking him, till he would 
fill the trough for them. In this case the horse that did the 
pumping associated in his mind the motion of the pump-handle, 
as he had seen it done by his master, with the supply of water. 
And while they associated this supply with his pumping, he 
knew what their teasing him meant, because he associated it 
with their motions about the trough, indicating so plainly that 
what they wanted was water. But I will give a still stronger 
case. A dog belonging to a Frenchman was observed to go 
every Saturday, precisely at two o’clock, from his residence, at 






MAN AND THE INFERIOR ANIMALS. 


859 


Relation between cause and effect learned from association. 


Locoyarne to Hennebon, a distance of about three quarters of 
a league. It was found that he went to a butcher’s, and for 
the purpose of getting a feast of tripe which he could always 
have at that hour on Saturday, their day of killing. It is als ( o 
related of this dog, that at family prayers he was always very 
quiet, till the last paternoster was commenced, and then he 
would uniformly get up and take his station near the door, in 
order to make his exit immediately on its being opened. The 
narrator of these facts thinks that the first fact shows, that the 
dog could measure time and count the days of the week. But 
this cannot be so. The dog undoubtedly associated in his 
mind the time at which he could get the tripe, with something 
that occurred on Saturday at that hour at his master’s house, 
just as he associated the concluding of family prayers with 
something that occurred as the last paternoster was read, per¬ 
haps with some peculiarity in the manner of his master when 
he came to that part of the service. 

546. Animals learn the relation between cause and effect by 
this mental association, and act upon the experience thus 
gained. This is manifest in the examples I have cited. And 
it may be observed in many acts that we witness occasionally 
in the higher animals. Thus, for example, as my horse was 
cropping some grass, he took hold of some that was so stout, 
and yet so loosely set in the ground, that he pulled it up by 
the roots, and, as the dirt which was on it troubled him, he 
very deliberately knocked it across the bar of a fence till he got 
all the dirt out, and then went on to eat it. Here was a 
knowledge of cause and effect which was derived from previous 
experience through mental association. You see the same 
thing when you see a cat jump up and open the latch of a 
door, or a horse unbolt the stable door to get out to his pasture. 
But in all such cases the knowledge of cause and effect differs 
from the same knowledge in man in one important particular. 
In the animal it is always an individual knowledge, that is, a 
knowledge of individual facts; while in man it is often a knowl¬ 
edge which has relation to general truths or principles. 

547. From the facts stated in the last few paragraphs it is 
clear, that Carpenter is not correct in saying, that “ the mind 
of man differs from that of the lower animals, rather as to the 
degree in which the reasoning faculties are developed in him, 
than by any thing peculiar in their kind? While there is much 
in common between them in their modes of mental action, es¬ 
pecially if man be compared with other animals in the period 




360 


HUMAN PHYSIOLOGY. 


Abstract reasoning source of language and of a belief in a Creator. 

of his infancy and childhood, there is, as you have seen, one 
attribute of the human mind which is wholly peculiar to it. 
and never exists in any degree in any other animal. And this 
attribute, the power of abstract reasoning, or in other words, 
the power of deducing general truths or Taws from collections 
of individual facts, constitutes the great superiority of the hu¬ 
man mind, in distinction from the mind of the brute. 

548. It is this attribute which is the source of language in 
man. This can be readily seen by observing what is the na¬ 
ture of language. It is a collection of corresponding vocal 
and written signs of an arbitrary character, arranged accord¬ 
ing to certain general rules or principles. Other animals do 
have a kind of language of a very limited character. It is 
the language of natural signs. It is composed of cries and 
motions, which vary in different tribes of animals, so that each 
tribe may be said to have its own natural language. But an¬ 
imals never invent and agree upon any arbitrary signs, as is 
done continually by mankind in the construction and exten¬ 
sion of language. This they cannot do, because abstract rea¬ 
soning is required for such an invention. General principles 
are observed in the construction and arrangement of arbitrary 
signs, and, as I have shown, brutes know nothing of principles. 

549. This attribute also is the source of man’s belief in a 
Creator. If he had not the power of deducing general truths 
from individual facts, he could neither discover the truth that 
there is a first great Cause, nor appreciate or even receive it, 
if it were communicated to him. Not the faintest shade of 
such an idea can be communicated to any of the inferior ani¬ 
mals, however high their mental manifestations may be, and 
simply because the structure of their mind is such that they 
know nothing of general principles. Carpenter speaks of the 
disposition to believe in the existence of an unseen but pow¬ 
erful Being, which is found to be universal even among the 
most degraded races of mankind, as a natural tendency, which 
he seems to think is implanted in the human breast by the 
Creator. But it appears clear, that it is a mere natural result 
of the exercise of the power that I have just spoken of. 

550. Man differs from other animals also in having a con¬ 
science, or, a knowledge between right and wrong, and a sense 
of obligation in relation to it. This moral sense is supposed 
by some to be a mere result of the exercise of the power of 
abstract reasoning. But others suppose that the sense is im¬ 
planted as a distinct quality or power, and that the office of the 




MAN AND THE INFERIOR ANIMALS. 


361 


Conscience. None in animals. Summary of mental distinctions. 


reasoning power in relation to it is to bring the evidence before 
it for its decision. I shall not discuss this point, but will merely 
remark in regard to this subject, that there is no doubt as to 
the existence of such a sense in man. Some attempt to throw 
doubt over it by pointing to its perversions, maintaining that it 
is a mere creature of circumstances, varying almost endlessly in 
different parts of the world. But it would be just as rational to 
attempt to show, that there is no such thing as a sense of the 
beautiful in man, by appealing to the evidences of perversions 
of taste, which ignorance, bad education, and foolish and nov¬ 
elty-loving fashion have induced. 

551. In those cases in animals in which this moral sense has 
been supposed to exist, it is nothing but slavish fear. It has 
been said by some one that man is the god of the dog; but it 
is sacred trifling to compare the attachment of an animal to its 
master and its fear of his displeasure, with the intelligent regard 
of man for his Creator as a holy and benevolent being. We 
ordinarily recognize the distinction between man and animals, 
as to the existence of a conscience, in the language we use. 
We never attach the idea of moral character to the acts of an 
animal except by the force of association, and then only slightly 
and loosely. We are not apt to speak of punishing a dog, for 
this word implies a moral fault as the occasion of the infliction. 
We ivhip him, sometimes, simply to associate in his mind the 
smart with the act done, so as to prevent him from doing it 
again, and sometimes to vent our ill feeling for the harm done 
us on the poor dog that has so innocently done it. It is related 
of Sir Isaac Newton that he had a favorite little dog called 
Diamond, who being left in his study, overset a candle among 
his papers, and thus burnt up the almost finished labors of many 
years, and yet the philosopher only said, “ 0 Diamond! Dia¬ 
mond ! thou little knowest the mischief thou hast done.” New¬ 
ton was both a wise and a good man, and while he saw that 
whipping the dog would do no good in preventing any similar 
accident in future, he had no ill feeling to vent on poor Diamond, 
who certainly had a better and more rational master than most 
dogs have. 

552. The mental distinction between man and animals may 
be thus summed up. The animal is governed by instinct, and 
in the higher orders by a kind of reasoning which is based upon 
mental association. Man has, in addition to instinct and this 
lower order of reasoning, the power of abstract reasoning. In 
the lower orders of animals probably instinct rules alone. In 

31 






362 


HUMAN PHYSIOLOGY. 


Experience gathered by animals, but not transmitted. 

them there is none even of the limited reasoning which we see 
in the higher animals. They have a nervous system with cer¬ 
tain central organs, but have really no one great central organ 
that we can call the brain. As we trace the animal kingdom 
upward, we soon find that a brain appears, that is, such an 
organ as may be considered the chief centre of the nervous sys¬ 
tem. And then, as we continue to trace upward in the scale, 
we find that the more intelligence or reasoning there is, the 
more prominent is the brain in proportion to other parts of this 
system. When we come to man the brain is much larger than 
in any other animal, and his intelligence is not only greater, 
but it is of a different character. Not only is the amount of 
his reasoning by association greater than in other animals, but 
there is also superadded, as his grand distinguishing mark, the 
power of abstract reasoning. 

553. Instinct, you have seen, cannot be improved by educa¬ 
tion. It always acts in the same way throughout the life of an 
animal, and through the succeeding generations of the tribe. It 
has no accumulated experience, either individual or traditional. 
But it is otherwise with the two kinds of reasoning power. 
These can be educated, and they have an experience. But here 
there is a marked difference between the two kinds of reason¬ 
ing. The lower kind of reasoning, that of mere association, 
which is the only kind possessed by animals, is altogether in¬ 
dividual, and is not at all traditional. However wise an animal 
may become, there is no transmission of his wisdom to his 
posterity. No animal can start from a point of knowledge 
gained by his ancestor, as a vantage ground, and thus make 
greater advances than his predecessors. Each animal, in ac¬ 
quiring experience as to the relations of cause and effect, has to 
begin at the beginning, and learn every thing for himself. The 
higher form of reasoning,' that which man alone possesses, is 
absolutely essential to the transmission of experience from one 
generation to another. It is necessary to the transmission even 
of that experience which is gathered by the other power of 
reasoning, as well as that which is gathered by itself. The 
amount of improvement which can be effected where there 
is only the lower kind of reasoning to act upon, is very won¬ 
derful in the case of some of the docile animals. The dog, the 
elephant, the monkey, &c., are familiar examples. By the 
skillful and persevering use of mental association in the training 
of animals, results can be obtained, that resemble very closely 
those which come from man’s power of abstract reasoning. 




MAN AND THE INFERIOR ANIMALS. 


363 

The power of generalization the basis of improvement in man. 

And in some cases the animal accumulates quite a large indi¬ 
vidual experience. But his race is none the wiser for it. It is 
none of it transmitted to another generation. 

554. We see then the basis of improvement in man. It is 
not his power of making inferences merely. The brutes do 
this. It is his power of making general inferences, or, in other 
words, deducing general laws or principles from individual facts. 
And as this power distinguishes man from the inferior animals, 
so a superior degree of it ordinarily constitutes the intellectual 
superiority of one man to another. This is seen very readily in 
inventions and discoveries. In the case of almost every inven¬ 
tion or discovery, the individual facts upon which it is based 
were known to many others, perhaps even a long time before 
the invention or discovery was made. The merit of the in¬ 
ventor or discoverer consists in having seen the available general 
truth indicated by the facts, and traced out its application to 
certain objects to be attained. Thus, to take a single example, 
dairymen and dairywomen in great numbers knew the fact, 
that a certain disease, .derived from the cow accidentally by in¬ 
dividuals, prevented them from taking the small pox; but 
Jenner was the first to see, that here was developed a great 
general fact, capable of universal application. And thus seeing 
the wide scope of the fact, he collected the proofs of it, and de¬ 
vised the means by which it could be made available to prevent 
the ravages of one of the great scourges of the race. It was 
by the generalizing power of his reasoning that he went beyond 
dairymen and dairywomen, and became the discoverer 

555. It is interesting to observe that while the capabilities 
of instinct are developed rapidly, sometimes almost instantane¬ 
ously, the capabilities of the reasoning power are developed 
gradually. Especially is this the case with the higher reasoning 
power, that distinguishes man from the brutes. The child is 
governed at the first wholly by instinct; and then as he gathers 
knowledge of the world around him through his senses, mental 
association comes into play. By the exercise of the lower kind 
of reasoning, which he has in common with animals, he accumu¬ 
lates experience of the relation of cause and effect. Thus far 
he is on common ground with animals, that is, those of the 
higher orders, except that he adds more largely to his experience 
from mental association than they do. Meanwhile the power 
of abstract reasoning is gradually developed, raising him up from 
the level of the brutes, and introducing him into companion¬ 
ship with the whole intelligent creation, even with God him- 





HUMAN PHYSIOLOGY. 


364 

The wonderful power of abstract reasoning. Slowness of development in man. 

self, whose image he bears in possessing this attribute. This 
power of generalizing facts is developed earlier than is generally 
supposed. It is of course feeble at first, and has a narrow 
range; but it very early shows itself sufficiently to indicate to 
us clearly, that the child’s mind differs essentially from that of 
the brute. And when disease or original physical defect pre¬ 
vents its development, we see the mental deficiency, and the 
consequent resemblance of the child in mental character to the 
inferior animals. 

556. When this characteristic power of the mind of man is 
fully developed, its achievements are often so wonderful, that 
they give us some realization of the great truth, that man is 
created in the image of God. As we witness the demonstra¬ 
tion of such facts as Newton discovered, or the unerring calcu¬ 
lations of an eclipse, or listen to a perfect argument as it develops 
grand truths, and leads us with a majesty of thought almost 
divine, straight on to mighty conclusions, we take in the full 
meaning of the assertion, that “the soul is that side of our na¬ 
ture which is in relation with the Infinite*’-’ and we see the folly 
of those dreamers in science, that look upon man as making 
merely the highest order in the animal kingdom. We see that 
the chasm between him and other animals is truly “ impassable.” 
We see that we are in a mental region of which the most intel¬ 
ligent of them know nothing—that though they live like us, 
having the same senses, seeing the same beautiful things, and 
hearing the same voices of nature, and like us have, thoughts 
and emotions and desires, they are shut out from an upper region 
of thought and feeling in which we freely roam, and from which we 
look with aspirations unknown to them to another world beyond. 

557. As the mental capabilities peculiar to man are slowly 
developed, so it is with his physical frame, and the powers that 
belong to it. Though man at length so excels all other animals, 
that they are subject to his power as their master, he is at the 
first the most helpless of all animals. He is a long time “in 
the nurse’s arms,” and for years he is unable to obtain his own 
food. lie does not reach the full strength of his body and 
mind till he is more than twenty years of age. He is in strong 
contrast with other animals in regard to this slowness of devel¬ 
opment, they generally reaching their full capabilities in a short 
time. But even among them, it is to be observed, that there is 
a difference in this respect, in obedience to a general law, that 
the higher the capabilities are, the slower they are in their de¬ 
velopment. 




MAN AND THE INFERIOR ANIMALS. 


865 


Difference between man and animals in physical endowments. 

558. The differences between the physical endowments of 
man, and those of the higher orders of animals, are often very 
minutely described. But though strongly marked, too much 
prominence is ordinarily given to them. They should be con¬ 
sidered as subordinate altogether to the mental differences. 
Thus, much is often said of the superiority of man in regard to 
the possession of a hand, on which I have remarked in various 
parts of this book. But why should he have such an instrument 
given to him ? Simply because he has a mind which is not 
only capable of directing it, but which needs such an instrument 
to produce suitable results in its action on the world around. 
If other animals had a hand they could not use it properly. 
r J hey have instruments of a different character, of less various 
capabilities, but such as are suited to their wants and powers. 
The same thing can be said of other bodily endowments. They 
are always suited in range and power to the wants and mental 
capabilities of the animal. As we trace out this general idea, 
we find that some animals have some bodily endowments which 
far excel the same in man. Thus, some have greater powers 
of vision and hearing than he has, because they need them. 
So, too, some have endowments of which we find no trace in 
man, as, for example, the power of flying. For the same reason 
most animals have special natural means of defense against the 
attacks of other animals; but man has not, because he has no 
need of them, as by his ingenuity he can contrive such means as 
he may require. 

559. The physical endowments of man in comparison with 
animals are indeed wonderful, and correspond with his spiritual 
endowments, so far as gross matter can compare with subtle 
immaterial mind. We have looked at these endowments in 
detail in various parts of this book. Let us glance at the prin¬ 
cipal of them collectively. As the muscles are the organs by 
which all communication between man and man, and indeed 
all action upon the external world is effected, it is in the endless 
combinations of muscular action that man is most signally su¬ 
perior to animals in physical endowment. This is shown, as 
you have seen, in the human hand, whether it be looked at as 
an instrument for w r ork or for expression. The same thing we 
see exhibited almost as strikingly in the muscles of the voice— 
both those which by their delicate and accurate action regulate 
the vocal ligaments, and those which by their complicated action 
give the voice all its variety of articulation, especially the latter. 
But let us look at the body as a whole. Man walks erect, a 

31 * 




366 


HUMAN PHYSIOLOGY. 


Beauty of the human form. Best shown when it is in action. 

significant characteristic of him as differing from animals. And 
though there be grace of movement in many animals, it is not 
in any case to be compared with that which we see exhibited by 
the erect human fornft The extreme variety of combination in 
the action of the muscles in mail is one cause of this superiority. 
But another and the chief cause is the impress of beauty given 
to graceful action by the mind. Almost all muscular action 
speaks to us a language that comes from the thought and feel¬ 
ing at work within, even when it is unintended; and this is the 
source of a large portion of the enjoyment that we receive, for 
the most part unconsciously, from the graceful movements that 
we witness in our fellow men. And when in a beautiful and 
graceful form we come to add to the ordinary movements of the 
body, which are commonly, though improperly, considered as 
meaningless, those movements which are distinctively express¬ 
ive of thought and emotion, we arc filled with admiration of the 
wonderful capabilities of the human frame in graceful action. 

560. The human form in repose, when in its greatest per¬ 
fection, far transcends, as a combination of varied beauty, any 
thing that we see in the inferior animals. But its superiority 
in this respect is best seen when the intelligent and feeling 
mind puts it into action. And this is especially true of those 
parts which are most engaged in expression—the hand with its 
endlessly varied movements, but most of all the face. It is in 
this noblest part of the human frame that the soul of man, 
through the subtle agency of the nerves, most strikingly imprints 
its immaterial qualities upon a material form, and exhibits the 
highest graces of motion in the delicate and ever varying play 
of the muscles. And when in the impassioned speaker, while 
the muscles of the voice and articulation are executing their 
exceedingly rapid and complicated movements, we see the whole 
frame in its motions and attitudes brought into consonance with 
the burning words and the beaming countenance, we take in 
the full idea of the adaptation of the human body to the mind 
that tenants it. Though the hand is commonly spoken of as 
affording the best illustration of man’s superiority to other ani¬ 
mals in muscular action, it is far from being as impressive an 
exhibition of it as this action of the whole frame. It is when 
the mind, through the numberless nerves that connect it with 
every part of the body, brings them all into its service in ex¬ 
pression, that we get the most exalted conception of the excel¬ 
lence of the human organization. 





VARIETIES OF THE HUMAN RACE. 367 


Mankind all the same species, but presenting very marked varieties. 


CHAPTER XIX. 

VARIETIES OP THE HUMAN RACE. 

561. Although, as we look at men of different nations, we 
find that there is a general agreement in form and organiza¬ 
tion, there are many points in which they strikingly differ from 
each other. “ With those forms, proportions, and colors,'” says 
Mr. Lawrence, “ which we consider so beautiful in the fine fig¬ 
ures of Greece, contrast the woolly hair, flat nose, thick lips, the 
retreating forehead, advancing jaws, and black skin of the negro; 
or the broad square face, narrow oblique eyes, beardless chin, 
coarse straight hair, and olive color of the Calmuck. Compare 
the ruddy and sanguine European with the jet black African, 
the red man of America, the yellow Mongolian, or the brown 
South Sea Islander; the gigantic Patagonian to the dwarfish 
Laplander; the highly civilized nations of Europe, so conspicu¬ 
ous in arts, science, literature, in all that can strengthen and 
adorn society, or exalt and dignify human nature, to a troop of 
naked, shivering, and starved New Hollanders, a horde of filthy 
Hottentots, or the whole of the more or less barbarous tribes, 
that cover nearly the entire continent of Africa;—and although 
we must refer them all to the same species, they differ so re¬ 
markably from each other as to admit of being classed into a 
certain number of great varieties; but with regard to the pre¬ 
cise number, naturalists have differed materially.” Cuvier ad¬ 
mitted but three varieties, the Caucasian , Negro , and Mongolian. 
The more commonly received classification, however, is that of 
Blumenbach, who makes five varieties, viz., the Caucasian, 
Ethiopian , Mongolian , American , and Malay. 

562. The chief characteristic of the Caucasian variety is the 
fine form of the head, it being nearly oval, as you view it from 
the front. It is also characterized by a great range of varia¬ 
tions of the color both of the skin and the hair. There has 
been more of civilization and improvement of every kind in this 
race than in any of the others. It is mentally superior to the 
other races. It is called Caucasian from Mount Caucasus, from 
the vicinity of which, it is supposed, it originated. Even at the 
preset day it is said that the characteristics of this race are 





3Q8 


HUMAN PHYSIOLOGY. 


Blumenbacli’s classification—most commonly received. 


most perfectly developed in tlie Georgians and Circassians, who 
live in the neighborhood of this range of mountains, and who 
are considered the handsomest people in the world. 

563. The Ethiopian variety is quite in contrast with the 
Caucasian. The organization has not the perfection and ele¬ 
gance which the Caucasian presents, and it shows an approxi¬ 
mation to the higher orders of the inferior animals. The skull 
is small. The forehead is retreating, while the face below is 
projecting, the cheek bones being prominent, and the nose 
broad. The apparatus of the senses is thus fully developed, 
while the brain is less than in the Caucasian. The hair is black, 
oily, and frizzled. It is commonly said to be woolly, but it is 
really not so. Dr. Carpenter says that “ microscopic examina¬ 
tion clearly demonstrates that the hair of the negro has exactly 
the same structure with that of the European, and that it doe3 
not bear any resemblance to wool save in its crispiness and its 
tendency to curl.” The skin is generally black; but not so in 
all the race, for the Caffirs and the Hottentots are yellow. 

564. The Mongolian variety, of which the Chinese race forms 
the largest family, is characterized by prominent broad cheek 
bones, flat square face, small oblique eyes, straight black hair, 
scanty beard, and olive skin. 

565. The American variety is characterized by high cheek 
bones, a narrow low forehead, features large and bold, except 
the eyes, which are deeply sunken in large sockets, hair gen¬ 
erally black, stiff* and straight, and complexion varying from a 
crimson brown to a deep copper. 

566. The Malay variety, which occupies the Islands south 
of Asia, in the Indian and Pacific oceans, has not so well marked 
characteristics as the other varieties. The complexion is brown, 
varying from a light tawny to almost black, the hair is black 
and thick, the forehead is low and round, the nose is full and 
broad, the nostrils wide, and the mouth large. 

567. Other classifications have been made, in some of which 
the human race is divided into many more varieties. Any 
classification must be in a great measure arbitrary, and must 
be regarded rather as a convenience, than as having the defi¬ 
nite and invariable character which belongs to truly scientific 
distinctions. In each of the five divisions of Blumenbach 
there is great diversity. Thus, in the Caucasian variety, the 
English, the French, the German, the Irish, <fec., are quite dis¬ 
tinct from each other. And we sometimes see very striking 
characteristic marks separating single families from others. The 




VARIETIES OF THE HUMAN RACE. 


369 


Differences in individuals, families and nations—produced by similar causes. 

varieties of the race are thus almost endless, the lesser differing 
only in degree from the larger. 

568. The national differences are evidently produced by 
causes of very much the same character with those which pro¬ 
duce differences in individuals and families. And the question 
arises whether such differences as those which Blumenbach de¬ 
scribes as marking the races, are not produced in a similar 
manner. This question has been much discussed, and there is 
great difference of opinion in regard to it. The great majority 
of naturalists believe in the unity of the origin of the human 
race, and hold that its varieties are the results of the various 
circumstances by which man has been surrounded. But some 
suppose that the different varieties come from separate pairs 
created by God in different localities, and hold that the history 
in Genesis is a history of the origin of only one of the varieties 
of the race. Those who advocate this doctrine are few in num¬ 
ber ; but it has acquired greater currency of late, because one 
of the most eminent naturalists of the present day, Professor 
Agassiz, has espoused it. His doctrine on this subject I will 
give as briefly as possible. 

569. All animals, he asserts, like plants, have particular lo¬ 
calities, for which they are fitted, and to which they belong. 
These zoological provinces, as he terms them, are of unequal 
extent, some animals having a wider range than others. From 
this general law of distribution, which he illustrates with many 
facts, he infers that the various animals on the face of the earth 
were not created in one part of the earth and distributed from 
this to other parts, but were created in, the provinces to which 
they belong. This view of the subject forces itself upon the 
mind of the naturalist, as he observes the arrangement of the 
various tribes of animals on the earth’s surface. And besides, 
there are apparently insurmountable difficulties in the way of a 
diffusion of animals over the globe by means of migration. For 
example, we cannot conceive bow the polar animals could have 
migrated over the warmer tracts of land, which they would 
have to cross according to this supposition, for it is impossible 
now to keep them alive under such circumstances with the 
greatest precautions. And farther, some animal's of the same 
species, sometimes presenting varieties and sometimes not, are 
found in different localities which are so cut off from all com¬ 
munication with each other, that it is impossible that these ani¬ 
mals could migrate from some one locality to all the rest. “To 
assume,” he remarks, “that the geographical distribution of 




370 


HUMAN PHYSIOLOGY. 


Doctrine of the multiple origin of the human race. 

such animals, inhabiting zoological districts entirely disconnected 
with each other, is to be ascribed to physical causes, that these 
animals have been transported, and, especially, that the fishes 
which live in fresh water basins have been transported from 
place to place—to suppose that perches, pickerels, trouts, and 
so many other species found in almost every brook and every 
river in the temperate zone, have been transported from one 
basin into another by freshets or by water birds—is to assume 
very inadequate and accidental causes for general phenomena.” 
Not only then were different species of animals created origi¬ 
nally in different localities, but it is also true to a considerable 
extent, that animals of the same species occupying different lo¬ 
calities were created in those localities. 

570. All this he claims to be consistent with scripture, and 
with very good reason. The account of the preservation of an¬ 
imals in the ark, interpreted according to the common license 
of language, indicates really only such a preservation, as would 
be necessary for the stocking of that part of the world where 
Noah and his family were, after the waters should subside 
The number and the variety of the animals preserved for this 
purpose would of course be very great, and would, according to 
the common usage of language in narration, be spoken of in 
the terms used in the Bible. This interpretation holds equally, 
whether the deluge be considered as having been partial or 
universal. 

571. The case being thus quite clearly made out in relation 
to animals generally, he proceeds to trace an analogy between 
them and the races of man in this respect. He supposes that 
there are certain zoological provinces for the different human 
races, as there are for the different species and varieties of ani¬ 
mals ; and that these races were separately created in these 
provinces with organizations suited to their peculiar localities. 
While he allows that climate and other influences affect the 
varieties of the human race, he claims that they are not com¬ 
petent to produce them alone; and he infers, therefore, that, 
there must have been, as in the case of animals, different original 
creations in the different zoological districts. He accordingly 
claims that the history given in Genesis is a history of the origin 
of only one branch of the human family. He does not sup¬ 
pose that the different branches constitute different species, but 
are made varieties of one species.* He characterizes mankind 


* The difference between species and varieties is this. The distinction of species rest* 
upon specific characteristics, that cannot be changed by those influences which tend tc 





VARIETIES OF THE HUMAN RACE. 371 


Most naturalists believe that the race came from one pair. 

as being every where essentially the same in mental character, 
and alike the accountable subjects of God’s kingdom, notwith¬ 
standing their multiple origin. It is in this respect that he 
considers them as being of one brotherhood, and he looks upon 
the expression in the Bible, “ made of one blood,” as being en¬ 
tirely figurative, and as referring to “ the higher unity of man¬ 
kind, and not to their supposed connection by natural descent.” 

I do not propose to go into a thorough discussion of this 
question. This would not be possible in the narrow limits of 
a chapter. I shall only present a general view of the chief 
facts and arguments that bear upon the point at issue. And 
let us look at this subject first in the light of physiology and 
natural history. 

572. The great majority of physiologists and naturalists, as 
I have before remarked, have thus far been of the opinion that 
the human race came from one origin, and that the varieties of 
it have been produced by the various influences to which man 
has been subjected. These are commonly included in the gen¬ 
eral expression, climatic and other influences. To be more par¬ 
ticular, they are—climate, situation, food, clothing, customs, 
habits, way of life, state of civilization. Too great prominence 
has been undoubtedly given to the influence of climate. Law¬ 
rence very justly remarks in his general conclusions in regard 
to the production of the varieties in man and animals, “that of 
the circumstances which favor this disposition to the production 
of the varieties in the animal kingdom, the most powerful is the 
state of domestication .” This word, as he uses it, includes all 
those social influences, which as manifestly affect the animals 
which man domesticates as they do man himself. The analogy 
between man and animals in relation to the results of the influ¬ 
ences referred to I shall soon speak of more particularly. 

573. That climatic and other influences do have a very great 
ageqcy in producing the varieties both individual and general, 
that we see on looking over the human family, no one doubts. 
The only question is, whether they have produced all these 
differences—whether, for example, they have occasioned that 


produce* the differences thnt make varieties. The characteristics of a species are orig¬ 
inal, while those of a variety are acquired. “The term species,” says Prichard, “in¬ 
cludes only the following conditions, namely, separate origin and distinctness of race, 
evinced by the constant transmission of some characteristic peculiarity of organization. 
A race of animals or of plants marked by any peculiarity which it has ever constantly 
displayed, is termed a species; and two races are considered specifically different, if they 
are distinguished from each other by some characteristic which the one cannot be supposed 
to have acquired, or the other to have lost, through any known operation of physical 
causes.” 







372 


HUMAN PHYSIOLOGY. 


Color affected by climate. Circumstances affecting the form. 

very wide difference that we see between the Caucasian and tlie 
Ethiopian. My limits will not allow me to go into a full exam¬ 
ination of the influence of these causes, and I can only touch 
upon a few points in a very general w T ay. 

574. That climate has a great influence upon the color of the 
race is proved by many clearly observed facts. Tropical heat 
always has a tendency to produce a black skin. This is shown 
very decidedly in the case of the Jews, who have preserved their 
characteristic features amid varieties of climate, and yet have 
their color altered. Thus, while the Jew of the interior of 
Europe has a fair complexion and light hair, under the scorching 
sun of India his hair is crisped, and his skin is black. The ev¬ 
idence of the influence of climate is the stronger in this case, 
because th§ change from the original color has been two-fold. 
For the original Jew in Palestine had undoubtedly a dusky skin 
and dark hair, upon which the temperate climate of the interior 
of Europe, and the tropical climate of India have produced two 
opposite effects. 

575. But in the varieties of the human race there are differ¬ 
ences of form as well as of color. That the various influences 
to which man is subjected have a marked effect upon his phys¬ 
ical form is universally acknowledged. We see this alike in 
individuals, families, and nations. Intellectual and moral influ¬ 
ences manifestly have some agency in moulding the shape of 
the head in the individual. The differences, which we so com¬ 
monly see in the shape of the head between the intellectual and 
the ignorant, are not owing altogether to original difference 
of capacity, but in part to education. The brain, like all other 
organs in the body, sis influenced in its development by the 
degree of activity to which it is stimulated. It is not made an 
exception to this general law of development. Accordingly we 
find that depressing influences tend to make the top of the head, 
tli3 cerebral part, small, and the forehead retreating, while the 
face, from the predominance of the sensual over the intellectual, 
is rendered relatively too prominent. The tendency of elevating 
influences is of an opposite character. And such influences, thus 
operating in the individual, when repeated and accumulated 
from generation to generation, produce great and lasting results. 
It is thus that a race becomes either degraded or elevated. By 
a continuance and accumulation of influences it acquires either 
a good or a bad fixed character. 

576. I have thus spoken of one class of causes effecting 
changes in the physical form, the influence of which is manifest 




373 


VARIETIES OF THE HUMAN RACE. 

Marked tendencies to three different forms of the head. 

But there are changes seen, the causes of which we cannot 
clearly make out; and yet we know that they are occasioned 
by the varying circumstances in which man is placed. By the 
compound influence of many causes combined we continually 
see differences in the shapes of various parts of the body intro¬ 
duced. Family and national peculiarities are thus occasioned. 
The influences to which I have thus referred, some of which are 
little understood, are all those which Mr. Lawrence includes in 
the term domestication , which, as I have before said, he applies 
to man as well as to animals. 

577. Dr. Prichard has pointed out three different types of 
form in the head, occasioned by three distinct classes of influ¬ 
ences. One he terms the prognathous, (a word derived from 
two Greek words meaning before and the jaw,) in which the 
jaws project very prominently forward. This formation is char¬ 
acterized by the predominance of the sensual over the intel¬ 
lectual, the apparatus of the senses being largely developed, 
while the cerebrum is small, making the forehead retreating. 
The tendency to assume this type is always in proportion to the 
action of the degrading influences. “Want, squalor, and igno¬ 
rance,” says Carpenter, “ have a special tendency to induce the 
diminution of the cranial portion of the skull, and that increase 
of the facial, which characterize the prognathous type.” It is 
seen most strongly marked in the negroes of the Gold Coast. 
In the pyramidal type, as it is termed, the cheek bones are very 
broad, and the bones above are so shaped as to give the top of 
the head a sort of pyramidal form. This type we see in those 
tribes that lead a wandering life—the nomadic races, as they 
are called. The oval or elliptical form, which is seen so -well 
marked in the Caucasian variety, is manifestly the result of ele¬ 
vating influences. These types are convertible into each other. 
Thus, the oval may be degraded into the prognathous, or the 
prognathous may be elevated into the oval. The latter change 
is seen in the Ethiopian, when in successive generations he is 
subjected to elevating influences, in his intercourse with the 
Caucasian. And it is interesting to observe that the form of the 
head is more readily changed than the color. “ Thus,” says 
Carpenter, “in some of the older West Indian colonies, it is 
not uncommon to meet with negroes, the descendants of those 
first introduced there, who exhibit a very European physiog¬ 
nomy ; and it has even been asserted that a negro belonging to 
the Dutch portion of Guinea may be distinguished from another 
belonging to the British settlements, by the similarity of the 






374 


HUMAN PHYSIOLOGY. 


Insensible gradations in diversity. Fixedness of the varieties. 

features and expression in each, to those which peculiarly char¬ 
acterized his master’s. The effect could not have been produced 
by the mixture of bloods, since this would be made apparent 
by alteration of color.” In the same way is the pyramidal type 
convertible with the others. The pyramidal and the progna¬ 
thous are often mingled together, by the influence of vagabond 
habits and degrading causes. 

578. The view thus given of the operation of influences in 
producing the varieties of mankind is strengthened by the fact 
that, as Humboldt says in his Cosmos, there are “many inter¬ 
mediate gradations in the color of the skin and in the form of 
the skull.” If we look alone at the extremes in varieties of color 
and form, we are of course disposed to regard such great differ¬ 
ences as marking a distinction of species. But when we see 
these varieties passing into each other by such insensible grada¬ 
tions, and at the same time observe the manifest influence of 
causes upon these gradations, as in the cases referred to in the 
last paragraph, the evidence is clear to us that the varied influ¬ 
ences brought to bear upon man are competent to produce the 
varieties of the race. 

579. But it is objected that although climatic and other in¬ 
fluences have a great ellect, yet, so far as we can see, they only 
produce changes that approximate to those differences that 
mark the grand divisions of the race. They cannot, for exam¬ 
ple, be shown, from actual observation, to have effected the 
entire change in any length of time of any portion of the Cau¬ 
casian race into the Ethiopian, nor, on the other hand, of the 
Ethiopian into the Caucasian. It is objected, farther, that the 
peculiarities of the principal varieties of man existed in the early 
history of the race. This appears in relation to the Ethiopian 
variety in the figures found on Egyptian monuments. These 
show that the peculiarities of the negro race were as strongly 
marked nearly 5,000 years ago as they are now. This fixedness 
of character under such a variety of influences continued so 
long, it is claimed, indicates that the peculiarities were original, 
and not acquired. 

580. In reply to both of these objections, I will call your 
attention to a general fact, which I deem to be very significant 
in its bearing upon the great point at issue. It is the fact that 
when a variety is formed by any influences, either among plants 
or animals, it is apt to remain in spite of opposing influences. 
It seems to be easier by far to produce a variety, than to bring 
it back to the character of the original from which it earner 




VARIETIES OF THE HUMAN RACE. 


375 


Influence of “domestication ” both in man and in animals. 

Domestication has been continually producing varieties in the 
animals that man has so largely appropriated to his service, and 
tne varieties once produced, commonly remain. And the same 
thing is seen in the varieties resulting from the /same class of 
influences so continually in the human race. It is matter of 
common observation that family and national peculiarities are 
apt to be perpetuated. And it is not merely from a continu¬ 
ance of the causes from which they result, for they are apt to 
remain even when strong counteracting influences are brought 
to bear upon them. Now the causes which tend to produce 
varieties in the human race acted of course at the first, and 
were competent to produce the most prominent varieties during 
the first ages of the race. And the tendency to fixedness, which 
we see exemplified in so many ways in the varieties of both 
plants and animals, is sufficient to account for the perpetuation 
of such marked characteristics as those of the Ethiopian and the 
Caucasian. 

581. The analogy then which is thus observed between man 
and the domesticated animals is a much clearer and stronger 
one, than that which Professor Agassiz has attempted to make 
out between man and animals generally .in regard to zoological 
districts. And the inference is a legitimate one, that the same 
influences, that we see produce varieties in domesticated animals, 
are competent to produce the varieties in the human race, which 
are even less marked than some of those which we see in ani¬ 
mals. Varieties are produced more readily and in greater 
numbers in animals than in man, probably because they have 
less power of resisting influences that act upon them. The va¬ 
rieties of some of the domesticated animals are very numerous. 

582. The analogy drawn between man and animals in regard 
to zoological districts is weakened by the consideration, that 
there was no necessity for man’s being created in different lo¬ 
calities, because he can migrate so easily from one country to 
another. The necessity existed in regard to plants and animals, 
but not to the same extent in all. Migration is easier in the 
case of some than in the case of others. And this difference 
seems to have been acted upon by the Creator. Accordingly, 
the evidence is quite conclusive, that those animals which have 
been so universally appropriated by man to his service, have 
been diffused from central points and have gone with man, 
instead of being created in many localities. This being the 
case, it is hardly to be supposed that man, who is capable, 
through his ingenuity, and skill, and daring, of going every 





376 


HUMAN PHYSIOLOGY. 


New causes occasionally introduced by the Creator. Facts showing this. 

where, would be unnecessarily created in different pairs at differ¬ 
ent points on the earth’s surface. 

583. But suppose that in view of all the evidence we should 
come to the conclusion, that the climatic and other influences 
are not the sole causes of the differences in the races, are we of 
course driven to the admission that, as Agassis and others teach, 
there must have been created at the first, several, we know not 
how many different pairs in different localities ? By no means. 
We are not to forget that the Creator, besides using influences 
of which we have no knowledge, (which he is continually doing,) 
can effect new combinations of the causes already existing, or 
introduce into operation entirely new causes. That he is from 
time to time evolving new results in one or the other of these 
ways, or both of them, is manifest. The very common notion, 
that at the creation all the causes which have produced all the 
phenomena that have been observed to the present time, were 
then set in operation, and have been left to work out their 
results, seems to be contradicted by many facts. Most of the 
causes then set in operation, it is true, have been at work ever 
since. Unless this were so, nature would not exhibit the regu¬ 
larity which it now does, and calculations could not be made 
with such definiteness as to its processes from knowledge gained 
by experience. But changes and irregularities sometimes occur 
which must have been the result of new causes. I shall allude 
to but a few examples. 

584. The age of man before the flood was much greater than 
it has been since. A change was effected at that period. It 
was not a mere arbitrary change, but such a change in the very 
character of the human system, that its capability of resisting 
the tendency to decline was greatly reduced in the period of its 
continuance. It was not a change resulting from the influence 
of deteriorating causes, for in that case it would have been less 
suddenly induced. To effect this change some new causes must 
clearly have been brought to bear upon the system, making it 
in the post-diluvian a different system in some important respects 
from what it was in the ante-diluvian. Take a fact of a differ¬ 
ent kind, indicating a similar change of agency. New diseases 
from time to time appear. This could not occur without eithei 
entirely new causes, or new combinations of elements heretofore 
existing. That very definitely marked disease, the small pox, 
we have the best of evidence, was not known to the ancients, 
and is comparatively a modern disease. It is impossible tc 
conceive of its being introduced without some new cause of a 




VARIETIES OF THE HUMAN RACE. 


377 


Supposition of new causes more probable than Agassis' supposition. 

very definite character. Take now another fact of a widely 
different kind from either of those to which I have alluded. 
The earth is marked all over with signs of great convulsions 
that have occurred since its first creation. It has been supposed 
till recently that these signs all refer to that great event de¬ 
scribed in the Bible, the Deluge of Noah; but geological 
researches have demonstrated pretty clearly that they point in 
part at least to other previous convulsions. Now these convul¬ 
sions are not to be reckoned as a part of the regular order of 
nature. They could not have resulted from the ordinary causes 
that act continuously. New causes must have been introduced 
at the time, to produce these unwonted results. 

585. It matters not to the argument above indicated, whether 
the new results that are occasionally developed, come from a 
direct agency at the time, or come from a chain of causes set in 
operation a long time before. The results are new results, and 
come from causes or combinations of causes, which differ from 
those that have produced the ordinary and regular results which 
we witness from day to day or from year to year. 

586. Now in like manner can we suppose, if it be necessary, 
that the Creator produced the varieties of the human race, by 
adding other and new causes to the ordinary influences to which 
man is subjected. This is a much more probable supposition 
than that of the advocates of the multiple origin of the race. 
For besides accounting satisfactorily for the facts, and at the 
same time being consistent with the record in Genesis, it is 
more clearly supported by analogical facts than the supposition, 
(for it is a mere supposition,) that the human race was created 
in different localities. And farther, this supposition avoids diffi¬ 
culties which attend the other. For, if we suppose that the 
race came from different pairs, it would be difficult to decide 
how many pairs there were. Such are the variations of the 
race in different localities that there would be much disagree¬ 
ment as to the number of the representative pairs, and their 
distinguishing characteristics. 

587. But it may perhaps be said in objection, that I am 
supposing a miraculous interposition. Whether it may rightly 
be termed such I will not stop to consider, but will merely re¬ 
mark, that it is just such an interposition, or rather, direct agency, 
as is affirmed by the advocates of a multiple creation, differing 
from it only in the time of its occurrence . They suppose the 
direct agency of God to be put forth in creation at different 
points, whether at different times they do not say, and this is 




378 


HUMAN PHYSIOLOGY. 


The testimony of the Bible to be received ns evidence. 

really quite immaterial; and I suppose the same direct agency 
to be put forth, but in a less marked manner, to produce a 
change in what has been already created. In supposing the 
direct agency of the Deity at all, we go beyond mere physics; 
and he surely has the power to put forth this agency at such 
times as he pleases.* 

588. But the supposition made above is not in my view 
needed. I believe that the regular, continuous, natural causes, 
which have ever operated upon man, have been competent to 
produce all the varieties of the race. And I only suggest this 
supposition, as a consideration for those who fail to see that 
these causes have been thus competent; and I claim that 
it is a more probable supposition than the one offered by 
Agassiz and others to meet the difficulty in the minds of such 
persons. 

589. Thus far I have treated this subject chiefly as one 
of natural history and physiology. But is the testimony of 
the Bible not to be received as a part of the evidence ? Is 
the question to be decided wholly on considerations and facts 
drawn from natural history and physiology ? This seems to 
be the view of some naturalists, though the great majority of 
them are disposed to admit the statements of Scripture as evi¬ 
dence. It is true that the Bible does not purport to be a phi¬ 
losophical book. Its language is based upon the principles of 
common and not scientific usage, and is so to be interpreted. 
And it should be thus interpreted in relation to the subject be¬ 
fore us. Its statements on this subject are of the most explicit 
character. It purports to give an account of the origin of the 
race, and portions of its history. It ascribes the corrupt char¬ 
acter of the race to a fallen parentage. This connection of the 
general corruption of the race with the fall of its original pair, 
however divines and philosophers may differ in accounting for 
it, is recognized as a fact throughout the whole book of revela¬ 
tion. The testimony is definite, and is not to be mistaken. 
The question is, whether it be valid testimony. And if the 
Scriptural record be established, as it is abundantly, by both 

* There seems to be in the minds of some naturalists a great reluctance to admit at all 
the direct agency of the Creator, whether it be exerted in consonance with the order of 
nature which he has established, cr miraculously in opposition to it. And they would 
smile skeptically at what they would deem the simplicity or superstition of Hugh Miller, 
in referring some narrow escapes which he has had, in pursuing his geological researches, 
to a particular Providence. The relation of the agency of the great First Cause to second 
causes, it is true, is a mysterious subject; but it implies no disposition to fathom what is 
unfathomable if we assert that the facts are far from warranting us in the belief, that this 
agency has not been exerted since the period of the creation, but confined itself to th»t 
time. 









VARIETIES OF THE HUMAN RACE. 


379 


The QTiity of the race recognized by the whole scope of the Bible. 

internal and coincident evidence, its testimony in regard to the 
origin of the race is to be received by scientific men. It can 
not be set aside by any mere presumptive and analogical evidence 
drawn *from physiology and natural history. If actual facts 
be proved inconsistent with the Mosaic history, as properly 
interpreted, they will of course bring discredit upon that his¬ 
tory. No immunity against a strict investigation is to be 
claimed for the Bible. But there is no fear of such an issue * 
and it is to be remembered that mere analogies are not facts, 
and are not to be deemed as having much force, especially when 
there is a question in regard to their value in comparison with 
other analogies that point to an opposite conclusion. 

586. If the account given in Genesis be a correct account, 
as is generally allowed by the advocates of the multiple origin 
•of man, and if, as they claim, it is the account of the origin of 
only one branch of the race, while other pairs were created in 
other parts of the world, they are driven by the facts in the 
case to this alternative. Either other pairs were created with 
an original corrupt nature, or they were created innocent as 
Adam and Eve were, and then were tempted in a similar man¬ 
ner and with a similar result. To claim that the other pairs 
were made so like Adam and Eve as to constitute with them 
one species, alike physically, intellectually and morally, without 
taking either of the suppositions just given, is to admit the 
truth of only a small portion of the Mosaic account, and is also 
inconsistent with the existence of the great acknowledged fact 
of the general corruption of the race. So that it is evident 
that the unity of the race, and the truth of the Mosaic history, 
must stand or fall together. And it is not the truth of this 
history merely that is involved in this question, but the truth 
of the Bible as a whole. For the corruption of the race, which 
the Bible seeks to remove, as before remarked, is throughout 
this book distinctly referred to the fall of man as recorded in 
the Mosaic history as its origin. The main facts of that record 
are recognized as true by the whole scope of the Bible, what¬ 
ever may be thought of the minute particulars of the narration. 
It matters not then, you wi^l observe, to the argument, whether 
the Mosaic account be received as true in all its minutiae, or 
whether it be considered, as it is by some, as a mere myth. 
For the argument is based upon the recognition by the rest of 
the Bible of the main facts contained in the history. And if it be 
a myth or fable, it must be based upon these facts, or, in other 
words, it is these facts that it is the object 01 this myth to convey. 





380 


HUMAN PHYSIOLOGY. 


Distinction between man and the higher animals very definite. 

587. I have thus presented a summary (for it necessarily is a 
mere summary) of what I deem to be the proper view of this 
subject., In doing so, I have left out many facts and considera¬ 
tions which are important, if we intend to go into a full and 
thorough investigation. I have selected for your consideration 
those points which are most prominent and important. I have 
attempted to indicate as clearly as I can the value of the differ¬ 
ent prominent arguments, that have been advanced on both 
sides of the question. And from the views and facts presented 
I think it very evident, that the true interpretation of the pre¬ 
sumptive evidence, drawn from natural history and physiology, 
is entirely in accordance with the teaching of the Bible, viz., 
that God “ made of one blood all the nations of men for to dwell 
on the face of the earth.” We are all one brotherhood. And, 
therefore, however debased our fellow man may be—to what¬ 
ever degree of degradation the unrestrained corruption of his 
nature may have brought him—we are to look upon him as 
containing the elements of that moral and intellectual elevation 
which is attained by the most gifted of men. It is this view 
of the subject that imparts dignity, and interest, and hope, to all 
philanthropic efforts to raise man from the moral, intellectual, 
and physical degradation, to which sin has reduced him. 

588. Although there are perhaps none at the present time 
who distinctly advocate the doctrine, that the lower races of 
men, as they are termed, are half way between man and such 
animals as the monkey and ourang-outang, yet there is in some 
minds an indefinite partial admission of this idea. There is a 
disposition in some naturalists to make the most of any resem¬ 
blances found between these races and animals. The attempt 
has been sometimes made to show, that there is a decided re¬ 
semblance between the form of the Ethiopian and that of the 
monkey tribe. But it has always failed. It has been said that 
the arm of the negro is longer than that of the Caucasian, and 
that in this respect he approaches to animals of this class. But 
the difference is so slight that the analogy fails entirely. And 
besides, the hand of the negro, the most important part of the 
upper extremity, bears no manner of resemblance to the imper¬ 
fect hand of the monkey, but is essentially like that of the 
European. It has been said, too, that the brain of the negro is 
like that of the monkey. The brain in any race or family of 
men that are debased and ignorant is smaller than in the ele¬ 
vated, and in this respect alone does it approach to that of the 
monkey and other higher orders of animals. And, as I have 









LIFE AND DEATH. 


381 


Life, though various in its manifestations, in some senses always the same. 

before said, there are certain mental characteristics in the most 
debased which link them to the most exalted of our race, creating 
an “ impassable chasm ” between them and the most intelligent 
of animals. 


CHAPTER IX. 

LIFE AND DEATH. 

589. Life is very commonly spoken of as being one thing, 
although its manifestations are exceedingly various in their 
character. In the simplest growths that we see, both in the 
vegetable and the animal kingdoms, the operations of life are 
in some respects very different from the complicated processes, 
that we witness in the human structure, which has been the 
subject of your study in this book. And yet, as you have seen 
in the Chapter on Cell-Life, life in these apparently opposite 
cases is essentially the same. It is the same in its origin. It 
begins always in a single cell, whether the living being is to be 
minute or monstrous, simple or complex, a plant or an animal, 
a creature of a day, or a being destined to immortality. Why 
it is that from a simple cell the vital force, as it is termed, can 
evolve such a range of diversified results as we see in all ani¬ 
mated nature, is one of the great mysteries of the Creator. As 
we see in the spring time a bud upon a tree unfold itself grad¬ 
ually, and develop to us successively leaves and flowers and 
fruit, it fills us with wonder, when we reflect how much has 
come from that little bud; but when we go farther, and think 
of the whole tree as having come from a single cell, so small 
that it can be seen only by the microscope, the mystery appears 
passing wonderful. And it is a still greater mystery, when a 
complicated animal organization is looked at as having been 
developed by the vital force, alike with all other living things, 
through a single cell as its origin. 

590. Life is not only always the same in its origin, but it 
continues essentially the same in its processes. All the various 
forms which it produces, both in the vegetable and animal 
world, are built and kept in repair by cells. All the functions, 
too, are carried on through the same agency. The secretions 






382 


HUMAN PHYSIOLOGY. 


Difference between the vital force, and heat, light, and electricity. 

and excretions, as you saw in § 201, are effected by constant 
successive creations of numberless cells. Even the intellectual 
operations in the mind of man are dependent upon cells so long 
as the mind is connected with the body. In thinking, as well 
as in muscular motion, cells are worn out, and must be replaced 
by other cells, which are continually supplied by the vital force. 

591. Life being thus wonderful in its operations, the inquiry 
arises, what can this mysterious agent be. With curious eye 
we watch its workings, but although we can learn some of its 
laws, its nature eludes our search. Then pressing the micro¬ 
scope into our service, we trace it back to its hiding place in a 
minute round cell containing a fluid; but simple as this prison 
is in which it is confined, it is more of a mystery than ever. 
The vital force, which begins here, and, enlarging more and 
more the sphere of its operations, developes gradually the simple 
or the complicated living form, as the case may be, has been 
classed by some with other forces, the nature of which we do 
not understand, as heat, light, and electricity. But it differs * 
from them entirely in some important points. While they act 
in connection with matter generally, both organized and unor¬ 
ganized, vital force is only seen acting in organized substances. 
While they diffuse themselves through all kinds of matter with 
more or less rapidity, the vital force has no power of diffusion, 
but is confined within certain limits. These limits differ in the 
different living substances. The vital force has the power of 
appropriating matter to itself within these limits. It does this 
by assimilation, as described in § 10. It has then the power 
of extension to a limited degree; while the other forces men¬ 
tioned have the power of diffusion, in some respects limitless. 

592. Another difference is this. While these forces, light, 
heat, and electricity, are lessened in power by being diffused, 
vital force is not lessened by extension. Heat, for example, if 
diffused is lessened at the point of its diffusion; but life is as 
energetic at its starting point after its extension as before, and 
even more so. It is, so to speak, self-generating, while the 
other forces are mere products. The vital force stands peculi¬ 
arly alone in this respect. The effects too, which this force 
produces, as it lays common matter under contribution, and 
fashions it in such diversified forms, have an infinitely wider 
range of variety than the effects of the other forces. 

593. We can thus trace the differences between the vital force 
or principle and other forces, but we cannot, as I have before 
said, discern its nature. We know not whether it be one thing 




LIFE AND DEATH. 


383 


Life in the blood. Vital laws control the chemical and mechanical. 

It is convenient to speak of it as being so. But we know not 
but that it may be a compound of endowments, or tendencies 
imparted to matter, and varying with the various forms of living 
substances. Some have supposed that the vital principle resides 
chiefly in the blood, and that this is the meaning of the passage 
in the Bible, “the life of the flesh is the blood.” That the 
blood has some vital properties is certainly true. These prop¬ 
erties are communicated to it as it is made from the food, and 
fit it to be the material for the construction and repair of the 
organization. And it is simply the fact, that the blood is the 
common material out of which all the diversified parts of the 
living structure are made, that is recognized in the language of 
Scripture on this subject. The same fact is embodied in an¬ 
other form in the remark of the French physiologist, that the 
blood is chair coulante , or running flesh. 

594. When the vital force appropriates to itself common 
matter in assimilation, it takes it away in part from the opera¬ 
tion, of certain forces which have had entire control over it. As 
long as it is common dead matter, it is wholly subject to the 
laws of mechanics, and of chemical action. But when it be¬ 
comes organized living matter, the laws of life take possession 
of it. The laws of chemistry and mechanics are not, it is true, 
annulled in relation to it. They still exert their influence, but 
under the control of vital laws. The force of gravity acts con¬ 
tinually upon the body ; but the living muscles are much of the 
time acting in direct opposition to it. The blood circulates on 
hydraulic principles; but the vital force furnishes the motive 
power, and keeps the blood from becoming solid and stopping 
up its channels. Chemical changes are going on in the stomach, 
the lungs, and at every point in the capillary circulation; but 
they are modified, controlled, by the vital principle, and are 
properly termed chemico-vital processes. 

595. The human body is made of materials that are exceed- 
ingly prone to chemical decomposition, and the degree of heat 
which is maintained is such as to favor this result; but the vital 
force not only holds the chemistry of the system in abeyance, 
but even presses it into its service. When life is destroyed, the 
laws of chemistry assume their full sway, and the process of 
decay begins. The very agencies which served, while under 
the control of the vital principle, to maintain the living organi¬ 
zation, now acting alone run riot, and work its destruction. 
Thus, that powerful agent, heat, existing in the body at the 
point of 98°, is necessary to the carrying on of the processes of 






HUMAN - PHYSIOLOGY. 


384. 

Change always attends life in action. Life sometimes dormant. 

life; but let life be destroyed, and the maintenance of this de¬ 
gree of heat would ensure a very rapid putrefaction. So too, a 
degree of heat which would rapidly putrefy a dead egg by 
quickening the chemical changes, would actively stimulate in a 
living egg those curious vital processes that produce at length 
the bird. During incubation the egg of the hen is kept for 
three weeks at a heat of 105°, and yet when the chicken is 
hatched all of the yolk that is left is unchanged. A dead egg 
would soon putrefy under such a temperature. 

596. The vital force exhibits its controlling power in an ex¬ 
traordinary manner in connection with that great force of nature 
to which I have just referred. Heat is very diffusive, and is 
exceedingly liable to change from varying circumstances. And 
yet the vital force maintains the heat of the body quite uni¬ 
formly at one point, although the agencies which tend to vary 
it are very numerous and effective. The production of heat in 
the system is a chemical operation, but the vital principle reg¬ 
ulates the quantity in the body very accurately, by providing 
for its escape in various ways, and perhaps by curtailing in some 
measure its production. 

597. Continual changes are effected by the vital force in every 
part of the body. In one sense death may be said to be taking 
place constantly, while life is as constantly generated, as the 
useless particles are separated and taken away, and the new 
ones are deposited in their place. While these changes are 
going on the vital force so operates as to maintain the peculiar 
shape and plan of every part, even during its growth. And as 
we look abroad over all the diversified forms of animated na 
ture, the accuracy with which this force works in the prescribed 
mould of each is very wonderful. This point I have commented 
upon in the first chapter, page 18, and will not dwell upon it 
here. 

598. While the vital force is in action there is constant 
change; but sometimes it is dormant. A seed in its quiescent 
state has life in it, ready to be waked into action by the proper 
excitants, air, warmth, and moisture. Seeds that were found in 
the excavations of Pompeii have shown that they retained their 
life during all this time, by shooting forth their germs as soon 
as they were exposed to these natural excitants of their growth. 
One of the most interesting cases of this kind is related by Dr. 
Lindley. “ I have now before me,” he says, “ three plants of 
Raspberries, which have been raised in the gardens of the Hor¬ 
ticultural Society, from seeds taken from the stomach of a man 




LIFE AND DEATH. 


385 


Mysterious connection of life with the soul. 

whose skeleton was found thirty feet below the surface of the 
earth, at the bottom of a burrow which was opened near Dor¬ 
chester. He had been buried with some coin of the Emperor 
Hadrian, and it is probable, therefore, that the seeds were six¬ 
teen or seventeen hundred years old.” 

599. A similar dormant condition of the vital force exists in 
a greater or less degree, as you saw in § 158, in the state of 
hibernation. So also, in cold climates, life is throughout al¬ 
most the whole vegetable world dormant during the period of 
winter, to wake to greater energy from the stimulating warmth 
of spring. In the human body, with the exception of some 
few very rare cases, life is always in an active state. Some 
portions, however, of the system are a part of the time dormant 
for the purpose of rest and repair. The brain and the muscles 
sleep; but during their sleep life is busy in the formative vessels, 
repairing their energies, and we may say, their textures also, 
which have been wasted by their labor. I will not dwell longer 
upon this interesting subject, but in leaving it I remark, that it 
is a very wonderful attribute of the vital force that it can, as 
in the case of the hibernating warm blooded animals, stop all 
its active operations, without damage to the machinery of life, 
and with such facility resign itself into a state of temporary 
inactivity. 

600. The most mysterious of all the circumstances in regard 
to the vital force is its connection in man with the immortal 
soul. The life and the soul are so intimately connected that 
some have considered them to be the same. But they are two 
distinct forces. They are in some measure indeed antagonistic to 
each other. For the soul, in using the machinery of the nerves 
and muscles occasions a wear and tear of the structure, which 
it is the office of life with its numberless cell-laboratories to re¬ 
pair. The soul and the vital principle are both present in all 
parts of the system, but not in the same sense. The vital 
principle is seen equally at work every where. It has no great 
central organ from which it sends forth its influence. But the 
soul is especially connected with the brain, and by means of 
the complicated nervous connections of this organ, it affects 
and is affected by all parts of the system. Its influence is thus 
an all pervading one. Every point of the living organization 
has thus a sort of telegraphic communication with the imma¬ 
terial soul. 

601. But there is another view of this connection of the soul 
and the vital principle. The soul is developed in and with the 

33 




386 


HUMAN PHYSIOLOGY. 


Natural limits of life. Decay. • 

living structure. It is not created by itself and -put into the 
body as a tenant. Its powers are developed while the vital 
force developes the powers of the physical organization. The 
two processes go on together. Nay more, the development of 
the soul is in a measure dependent upon the development of 
the body. The vital force exerts a manifest influence upon the 
soul’s growth. As it prepares the organs for the use of the 
soul—those organs by which it acquires knowledge from with¬ 
out, and thus procures the stimulus and even the material for 
its growth—whenever the vital force fails to construct these 
organs properly, the powers of the soul are not well developed. 
This we see exemplified in the idiot. In this intimate connec¬ 
tion of the soul with life we find a great mystery. Life, a force 
belonging to mere matter, an endowment of it, or a compound 
of its endowments—life, that builds up all organized substances, 
the humblest and simplest vegetable growth, as well as that 
most complex of all living structures, man—life, that so soon 
perishes in the noblest of its works that it is likened to the dis¬ 
solving vapor—is made by the Creator an agent in developing 
an immaterial principle or being, that is to survive the dissolu¬ 
tion of the structure in which it is generated, and is to live 
forever. Strange that the immortal should be thus produced 
in the mortal—that the unchangeable and imperishable soul 
should be thus developed in such intimate connection with the 
changeable and perishable body. It is a mystery which we 
cannot fathom. 

602. The vital force, that is so busy in building and repair¬ 
ing so long as it lasts, has in all cases its natural limit; and in 
the case of the human system it seldom fully reaches this limit. 
The diversified, and complicated, and beautiful structures which 
it evolves, if saved from accident till the natural period of de¬ 
cline comes, lose their vigor and beauty, and at length die and 
are given up to the action of the common laws of chemistry, 
which the vital force has so long resisted and controlled. The 
structures then decay, and the particles are dissipated, perhaps 
to be united again to other structures. 

603. The death of the body is not ordinarily complete at 
the moment when what we term death occurs. Though as a 
whole, as a system of organs, the operations of life are at an 
end, yet there is some degree of life in spme parts, and there 
may be in all parts of the body. The beard and nails even, 
may grow. Some of the organs may secrete their fluids—the 
liver its bile, and the stomach its gastric juice. Some of the 




LIFE AND DEATH. 387 

Systerfric and molecular death. Death beginning in the heart, and in the lungs 


properties of life, too, manifestly still remain. The irritability 
of the muscles, which is strictly a vital property, as it never 
belongs to common dead matter, still appears on the applica¬ 
tion of excitants. It was the contraction of the muscles in the 
leg of a dead frog on the accidental application of a stimulus, 
that led Galvani to his grand discovery. And it is through 
this vital property that the culprit who has been hung can be 
galvanized into apparent life. Death then may be said to bo 
of two kinds— systemic, that is, the death of the body as a 
whole, a system of organs—and molecular , that is, the death 
of the individual molecules or particles which compose the 
body. Death can be said to be complete only when the laws 
of life have resigned their power over these molecules, and the 
laws of purely chemical action have taken their place. When 
this change occurs, the process of decay, which is strictly a 
chemical process, begins. 

604. It will be interesting to notice here the modes in which 
systemic death occurs. There are three great systems in the 
body, each of which is immediately essential to the continuance 
of life—the system of the circulation, the respiratory system, 
and the nervous system. And we may speak of death as be¬ 
ginning in any one of these systems when the cause of death 
acts primarily upon it. I will notice some examples under each 
head. 

605. If a large quantity of blood be lost, so large as to result 
fatally, death in this case obviously begins in the circulation. 
The heart not being supplied with the quantity of blood that 
usually flows through it, becomes more and more feeble in its 
action, till it at length ceases to beat. When a large aneurism 
bursts, it is the sudden drain from the circulation that destroys 
life. 

606. Any thing which to any great extent prevents the air 
from entering the lungs may cause death to begin in the respt 
ratory system. This may be done by three classes of causes. 
1st. Causes that act upon the large air passages. Examples 
of this class of causes are strangling, smothering, drowning, 
&c. In croup the principal cause of death is the prevention 
of the free passage of air through the windpipe into the lungs. 
2d. Causes which act upon the walls of the chest. If a bank 
of earth fall upon a man, though it leave his head clear, so that 
the air passages are unobstructed, he cannot breathe, because 
his chest is held as if in a vice. A man came near dying from 
this cause, who was having a cast taken of the upper part ol 





388 


HUMAN PHYSIOLOGY. 


Death beginning in the nervous system. 

his body. If the muscles of respiration were to be paralyzed, 
death would ensue, just as it does when they are prevented from 
acting by other causes. 3rd. Causes acting upon the lungs. 
Disease may occasion an amount of obstruction in the very 
substance of the lungs sufficient to cause death. It does so by 
preventing the introduction of-the air into the minute air vessels, 
where the air revivifies the blood. The obstruction is just as 
effectual in this case as it is where it occurs in the large air 
passages. 

607. When death occurs from a blow upon the head as the 
immediate result of the shock, we have an example of death 
beginning in the nervous system. But the cause may act upon 
this system in some other quarter. A blow at the pit of the 
stomach, for example, may so shock the whole nervous system 
as to stop at once the operations of life. Some poisons, too, as 
opium, destroy life by tlieir influence upon this system. Very 
extensive burns give a shock to the nerves from which they do 
not rally. The same can be said of other injuries when there 
is no recovery from the first shock. Powerful medicines, im¬ 
properly given in cases of disease disposed to prostration, may 
depress the nervous system to a point from which it may never 
revive. Cold destroys life mostly by the benumbing, paralyzing 
influence which it exerts upon the nerves. 

608. Though we thus classify the modes of death, in the. 
great majority of cases death is a complex event, resulting from 
a concurrence of causes. It is so even when the disease is not 
of a complicated character. Take, for example, a case of pure 
uncomplicated consumption, in jvhich all the organs but the 
lungs are in a healthy state to the end. The whole system 
becomes at length exhausted by the disease. If this exhaustion 
alone be the cause of death, then we may say that it is an ex¬ 
ample of death beginning in the nervous system. But if the 
obstruction in the lungs to the admission of air in the air-cells 
be the cause, it is a case of death beginning in the respiratory 
system. Generally in such cases death results from the two 
causes combined, and it is often difficult to determine which is 
the more prominent cause. 

609. The signs of death are so clear that there is, with very 
few exceptions, no mistake in regard to the occurrence of the 
event. The stories that are related about burying alive are 
most of them unfounded. The apprehensions created by them 
in the minds of some persons have led them to insist, that no 
body ought to be committed to the grave, till the most infaili- 






LIFE AND DEATH. 


389 


The signs of death. Death as viewed by the Physiologist, and the Christian. 

ble sign of death, putrefaction, has appeared. That we should 
wait for the appearance of this sign in all cases in which there 
is a shadow of doubt, I will allow. But the cases are exceed¬ 
ingly rare in which we cannot determine the reality of death 
long before this sign shows itself. Our decision is not made 
up, it must be observed, merely from the signs of death. All 
the circumstances of the case are taken into view—the disease, 
its progress, its symptoms, and the events of the last hours of 
the patient. With this evidence before us, we absolutely know, 
in all ordinary cases, that death has occurred when the respi¬ 
ration and the circulation have ceased. And in the exceed¬ 
ingly few cases in which there is any reason to doubt on that 
point, there is always something which will attract the attention 
and excite the curiosity of some one, unless there be stolid in¬ 
difference and the most absolute lack of intelligence. In such 
cases there is always something strange—the circumstances 
attending the cessation of the respiration and circulation are 
singular, and the signs of death are not complete and in their 
proper order of succession. Whenever there is for these reasons 
any doubt as to the reality of the apparent death, the strictest 
watch should be maintained till the signs of commencing putre¬ 
faction appear. With this simple rule of prevention burying 
alive need never to occur. 

610 . The investigations of physiology, as you have seen, end 
with the death of the body. It can give us no light on the 
question as to what may be beyond this life. Although the 
physiologist studies the human structure not merely as an or¬ 
ganization instinct with life, but also as the wonderful machinery 
through which a reasoning soul acts and is acted upon in this 
state of being, yet, as a physiologist, he knows not that the 
soul survives the death of the body. He knows not but that 
it is a mere endowment of matter, as life probably is, and so 
perishes in the hour of dissolution. He may indeed conjecture 
that such exalted faculties which are in this world susceptible 
of such high cultivation, instead of being destroyed with the 
body, are destined to still farther development in another state 
of existence. But what is mere conjecture to him as a Physi¬ 
ologist, is made fact to him as a Christian. The eye of his 
faith sees an immortal spirit rise from the dying body, and he 
realizes the truth of the sublime declaration, that “death is 
swallowed up of victory.” 




390 


HUMAN PHYSIOLOGY. 


Sources of our knowledge of hygiene. 


CHAPTER XXI. 

HYGIENE. 

611. It seems appropriate that the concluding chapter of 
this book should be on Hygiene. After having considered 
the construction of the machinery of the human system and 
the uses which the mind makes of it, one naturally inquires 
what are the conditions on which the full development of 
this complicated machinery and its daily repair depend. 

612. The principles and rules of Hygiene are to be 
learned from two sources. 1. They are to be learned from 
Physiology. As we observe the functions of the different 
organs, we can learn what those circumstances are which 
favor their due performance, and what those are which in- 
terfere with it. 2. They are to be learned, also, by observ¬ 
ing the effects of those agencies which are known to 
interfere with the functions and to produce disease. An 
exemplification of these two modes of learning the principles 
of Hygiene in relation to a single point will suffice. The 
study of the physiology of the chest shows us that nature 
has, in the construction of its framework, especially provided 
for giving ample room to the lungs; and so we deduce a 
law of Hygiene, that the chest should not in any way suffer 
compression. This is the first mode. But the same law 
can be deduced by the second mode, that is, by observing 
the results of compression of the chest. 

613. Rules of hygiene generally have but little practical 
influence, unless the physiological facts upon which they are 
based are understood. Although the evil effects of their 
violation may be vividly portrayed, and even illustrated, as 
in the case of the chest, by engravings, the impression upon 
the mind is by no means iis thorough and practical, as when 
the same lesson is enforced by a clear knowledge of the 
functions and arrangements of the organs and the conditions 
necessary to their healthy action. Physiology, therefore, 
should be studied as preparatory to a proper appreciation of 
Hygiene. 

614. Not only is a knowledge of Physiology essential to 
a proper appreciation of the rules of Hygiene, but in many 




HYGIENE. 


391 


Hygiene of digestion. Quantity of food to be eaten. 

cases they cannot be fully understood in their varied appli¬ 
cation without such a knowledge. With the very partial 
and superficial knowledge of Physiology that is usually 
communicated with Hygiene, these rules are for the most 
part mere arbitrary rules. And just so far as the principles 
on which they are based are not understood, is there a 
liability to mistake their application under various circum¬ 
stances. 

015. In considering the subject of hygiene, the natural 
division of Physiology, stated in § 57, should be kept in 
mind. There is a hygiene relating to the construction of the 
machinery of the body, and there is also a hygiene relating 
to the uses of this machinery. Besides, each organ has to a 
certain extent its own hygiene. And yet, as all the organs 
are connected more or less together in sympathetic action, 
there is a general hygiene of the system. I shall observe 
for the most part the same natural order that I followed in 
developing the subject of Physiology. I shall first treat of 
the hygiene of the construction and repair of the system— 
that is, the hygiene of digestion, circulation, respiration, and 
formation and repair. You can recur to a summary of these 
functions given in § 69. I shall then pass to the considera¬ 
tion of the hygiene of the uses of the machinery thus con¬ 
structed and kept in repair. 

616. Many of the points in the hygiene of the digestive 
organs have been already noticed in the physiology of diges¬ 
tion. I .need say nothing more in addition to what is said 
there of the importance of the thorough mastication of food, 
and of its having a due amount of saliva mingled with it; 
of the evils resulting from eating too fast, from eating be¬ 
tween meals, and from eating a great variety of food; and 
of the influence of exercise upon the process of digestion. 
There are some other points, however, that remain to be 
noticed. 

617. No very precise rules can be given as to the quan¬ 
tity of food that is proper to be eaten. But a consideration 
of the physiological principles of digestion suggests rules 
that are sufficiently definite for practical purposes. There 
must be such an amount of food as will furnish sufficient 
chyle to keep the blood, the building material of the body, 
in proper quantity. The question arises, how we shall 
know what amount of food is requisite for this purpose 
Fortunately, the want of the system and its supply are com 








392 


HUMAN PHYSIOLOGY. 


Miit&kes as to quantity of food. Length of intervals between meals. 

monly quite accurately indicated by the sensations as stated 
in § 87. The proper hygienic rule then on this point is, 
that we should cease to eat when the sensations created by 
the want of the system are removed—that is, when the 
hunger is appeased, and the accompanying feeling of discom¬ 
fort is succeeded by a feeling of agreeable ease. 

618. But there are mistakes often made in regard to these 
sensations. They may be prevented from making a true 
report. Thus, when eating is done too rapidly, more food 
than is needed may be introduced into the stomach before 
the sensation of ease and satisfaction is experienced. It is 
only when suitable time is given to mastication, and the 
food is rather gradually introduced, that this sensation forms 
the proper limit of eating. Again, there is a very common 
mistake in substituting the feeling of fulness for the sensation 
alluded to, as indicating the time for ceasing to eat. Those 
who adopt this false rule generally make the stomach tc 
bear as much as it can without absolute discomfort, and 
many daily overreach this point. The result is, that this 
organ soon gives out under this daily overworking ; or, if 
the stomach be a strong one, an injurious repletion is pro¬ 
duced in the system. Even in the latter case, the stomach 
at length gives out, and becomes the seat of disease. But it 
is astonishing how much labor, in the work of digestion, this 
organ will perform in some cases. 

•619. Too little food is sometimes taken. Poverty is 
commonly the cause. But sometimes it arises from false 
notions; as, for example, the notion that the quantity of 
food should be regulated by weight, or the more common 
notion, that we should rise from a meal with some amount 
of appetite remaining. The result is, that there is not a 
sufficient supply of chyle to meet the wants of the system. 
The wear and tear create a demand which is greater than 
the supply, and the body therefore loses its fulness and its 
vigor. 

620. In determining the length of the intervals between 
the meals, we should have regard to the time required for the 
completion of the process of digestion, and to the wants of 
the system. Some articles are digested more rapidly than 
others, but it commonly requires from three to four hours 
to complete the digestion of a meal. When the system is 
in a state of action, its want of food, as indicated by its 
sensations, shows itself a little time after the completion of 







HYGIENE. 


893 


Regularity of meals. Quality of food. Influence of the mind on digestioa 

the process of digestion. The interval, then, between the 
meals should not vary much from four hours. If it be made 
longer than five hours, some degree of exhaustion results; 
and if it be less than three hours, disturbance of the diges¬ 
tive process may occur, from having the digestion of one 
meal begin before that of the previous one is fairly finished. 

621. It is important that the meals should be eaten at 
regular periods from day to day. For the stomach, with its 
times of work and of rest, naturally contracts regular habits, 
a disturbance of which is injurious. This obedience to habit 
in this organ is manifest whenever any change is made in 
the time of eating. 

622. The question is often asked, whether such and such 
an article “ is healthy,” as if there were essentially different 
degrees of suitableness in different articles of diet. So far 
as digestion is concerned, any article is healthy to any in¬ 
dividual whose stomach can digest it without difficulty. An 
article may be perfectly healthy to one, and unhealthy to 
another. There are sometimes wide differences in this re¬ 
spect, owing to unaccountable peculiarities. But even in re¬ 
gard to ordinary differences, the question as to the propriety 
of any article of food is wholly an individual question. 

623. Our food should be varied in the different seasons 
of the year to a greater extent than is commonly done. In 
the warmer seasons it needs to be less stimulating, less heat- 
producing than in the colder seasons. The fruits, each in 
its season, should form regularly quite a large proportion 
of our food in the warmer months. If used thus, and not 
irregularly, as is commonly the case, they will tend to pre¬ 
vent, rather than induce, the complaints peculiar to that 
portion of the year. 

624. The state of the mind has much influence on the 
digestive organs. This is sometimes strikingly exhibited in 
the loss of appetite on the sudden reception of bad news. 
It is also seen in the influence of continued sorrow upon the 
appetite and the digestion. It is not strange, then, that one 
of the prominent causes of dyspepsia is mental disturbance 
or depression. And a cheerful mind is very properly 
deemed to be essential to easy and thorough digestion. 

625. In order to understand fully the hygiene of respira¬ 
tion , it must be borne in mind, that the great object of this 
function, as stated in § 131, is to bring the air into all the 
minute air-cells of the lungs, that it may change the blood 




894 


HUMAN PHYSIOLOGY. 


Compression of the chest. Importance of a good supply of pure air. 

which is sent there for this purpose. Anything, then, which 
interferes with the free introduction of the air into these 
cells is a palpable violation of the laws of health. And yet 
this interference is so commonly practised, that it is one of 
the prominent causes of disease. 

626. This interference is effected in two ways. It is done*, 
first, by mechanical compression of the chest. Althoug 
as I have shown in the chapter on the Respiration, therg 
are special pains taken by the framer of our bodies to pro¬ 
vide, in the construction of the chest, for the free introduc¬ 
tion of air into the lungs under all circumstances, this is 
often prevented by certain prevalent modes of dress. It 
must be observed that in the arrangement of the chest, a 
free motion of its walls in the expansion of the lungs is con¬ 
templated. The dress, there fore, should always be so loose as 
to admit of this free motion. If it is not, the air is not freely 
admitted to all the air-cells, and therefore the blood is not as 
fully changed, as nature requires; and the health is impaired 
just in proportion to the degree in which the due expansion 
of the chest is prevented. I have said so much on the re* 
suits of this compression of the chest in the chapter on 
respiration, both in this book and in my “ First Book on 
Physiology,” that I will only say here, that in this country 
it is one of the most prominent causes of disease among 
females. It not only produces disease in the lungs, but, by 
preventing these organs from effecting fully the requisite 
change in the blood, it impairs the quality and lessens the 
quantity of this building material, and thus diminishes the 
nutrition and the vigor of the system, and therefore renders 
it liable to a great variety of diseases, especially those of 
which debility is a prominent characteristic. 

627. The free introduction of pure air into the lungs is in¬ 
terfered with, secondly, by cutting off its supply. As you 
learned in the chapter on respiration, the oxygen of the air 
is used up in large quantities by the lungs, and the carbonic 
acid gas thrown off takes its place. If, therefore, there be not 
sufficient provision for the supply of fresh relays of pure air, 
a mixture of air and carbonic acid gas will be introduced 
into the lungs at every breath, so that there will not be 
sufficient oxygen to effect thoroughly the change in the 
blood. In this respect, therefore, the result is the same as 
when too little air is admitted by reason of compression of 
the chest. A portion of the requisite quantity of pure air 





HYGIENE. 395 

Bad results of defective aeration seldom appreciated. Hygiene of the circulation 

is shut out, in one case by diminishing the capacity of the 
chest, and in the other by having the lungs in part occupied 
by carbonic acid gas. 

628. The influence which this defective aeration of the 
blood, occasioned by these two causes, exerts upon the 
health, is seldom appreciated. For unless the deficiency be 
very great, no immediate obvious result is produced. But 
though the deficiency may be comparatively small, if it be 
continued from day to day for a long time, the aggregate 
result of this steady depressing influence is a serious one. 
Idle destruction of health and of life that comes from this 
imperceptible agency in every community is vast in amount. 
But most persons seem to be insensible to this fact. They 
need a narrative of such a destruction of life as occurred in 
the Black Hole at Calcutta, to convince them that a consider¬ 
able quantity of fresh air is required by every pair of lungs. 
And it is only by a description of an examination after 
death of some one who has been killed outright by extreme 
compression of the chest, that they can be made sensible of 
the need that the lungs have of the room that nature has 
given them. And even then the impression seems to be a 
momentary one. If all the injury that is done by defective 
aeration of the blood could be visibly traced out, we should 
then realize the necessity of having just as many of the 
air-cells, those little chemical laboratories, as nature de¬ 
signed, and of keeping them well supplied with the fresh air 
which they require for the life-giving work that they per 
form. 

629. The hygiene of the circulation need not detain us 
long. The office of the organs of the circulation is to circu¬ 
late the blood, the building material, everywhere. They 
never rest from their work. But they work more actively 
when the muscular system is in action than when it is at 
rest. As one lies in bed, the circulation goes on steadily, 
but quietly. But on rising and moving about, the circula¬ 
tion becomes more active. Not only does the heart oeat 
more quickly, but the capillaries in every part of the body 
increase their action. And, as more blood is carried to 
every part, there is more done everywhere. We see this 
in the skin, in the increase of the perspiration on exercise. 
When the muscular effort is very great, the excitement of 
the circulation is violent and tumultuous. The heart beats 
strongly and rapidly, ancj the flushed face shows how 




HUMAN PHYSIOLOGY. 


Exercise necessary to health. 

active is the circulation in its extreme vessels, the capil¬ 
laries. 

630. The occasional excitement by active exercise 19 
absolutely essential to the proper development of the body. 
It may sometimes, indeed, maintain its proper bulk in a con¬ 
tinued state of muscular inaction ; but its textures will not 
have the requisite strength and tone. That they may have 
these qualities, it is necessary that the blood be often pump¬ 
ed into their capillaries with the force that is given to the 
heart by active exercise. It is not the muscles alone that 
are rendered stronger and firmer by exercise, but the same 
effect is produced in all the textures, the bones, the liga¬ 
ments, the veins, the skin, &c. The great internal organs 
of the body are firmer, more fit to perform their duty, and 
less liable to disease, if the circulation in them is excited 
daily by this means. Active exercise makes the stomach 
digest better, the lungs perform the work of aerating the 
blood more thoroughly, and the brain serve the mind more 
easily and effectually ; it therefore renders one less liable to 
dyspepsia, to consumption and other diseases of the lungs, 
and to apoplexy and other diseases of the brain and the ner 
vous system. 

631. But the activity of the circulation may be made sc 
violent by exercise as to do some damage. Though its or 
gans are capable of bearing much in this respect, there is 
some need of caution. Harm is undoubtedly often done i# 
trials of strength when the effort is both violent and prolong¬ 
ed. Vigorous action answers fully the purpose of developing 
power and firmness; but violent action is attended with some 
hazard. 

632. In considering the hygiene of formation and repair , 
it must be borne in mind that there is constant change 
everywhere in the system. Particles that have become 
useless in the textures are continually taken up and carried 
away ip the veins or the lymphatics, and other particles are 
put in. their places, being taken for this purpose from the 
blood in the capillaries. This change is going on during all 
the period of growth, as well as afterwards. The health 
and vigor of the textures, and therefore of the system as a 
whole, are dependent upon the proper performance of this 
constant process of removal and fresh supply. 

633. There are two conditions necessary to the due per¬ 
formance of this process. The first is, that the blood, tho 






HYGIENE. 


397 


Necessity of a free discharge of the waste. Functions of the skin. 

universal material for building and repairing, shall be of 
good quality. This is secured when the digestive process, 
which furnishes the blood, is well performed, and the lungs 
and other organs, that purify the blood by discharging its 
refuse matter, are in good condition. The second condition 
is, that the blood shall be often quickened in its course 
through the organs by the excitement of exercise. This I 
have already mentioned in speaking of the hygiene of the cir¬ 
culation. 

634. The necessity of having the waste matter that is 
brought back from all parts of the body in the venous blood, 
effectually discharged by the various organs designed for 
this purpose (§178), requires a particular notice. The lungs, 
the skin, the liver, the kidneys, &c., must thoroughly eva¬ 
cuate this waste, or its retention will impair the quality of 
the blood, and thus interfere with the proper nutrition of 
the body, or, in other words, with the process of formation 
and repair. And the retention of this refuse in any consid¬ 
erable amount is immediately productive of disease. 

635. The lungs, while they take in oxygen from the air, 
discharge carbonic acid gas, that part of the waste of which 
it is their duty to rid the system. If this carbon be retain¬ 
ed, the blood is impure in proportion to the degree of reten¬ 
tion. 

636. It is the duty of the skin to discharge some portion 
of the refuse of the system in the sensible and insensible 
perspiration (§180). The skin is not a mere covering of 
the body, but it is also an active organ, performing very 
important functions. It continually discharges through its 
numberless pores a large quantity of matter. Although 
this matter is mostly in an insensible form, if from inactivi¬ 
ty of this organ it fail to be discharged, its retention renders 
the blood impure, and so does injury to the system. At 
least two pounds of matter are discharged from the skin in 
twenty-four hours. This being the case, it is not at all won¬ 
derful that activity of this organ should be so necessary to 
health, and that the suspension of its secretions should have 
so much influence in the production of disease. 

637. In the chapter on respiration, you learned that the 
heat of the body is produced by the change that takes place 
in the blood in the capillaries, as it receives the waste par¬ 
ticles, and as the new are deposited in their places. This 
change makes a real combustion in every capillary. The 

34 





398 HUMAN PHYSIOLOGY. 

Animal heat. Conditions. Body comfortable only when giving off heat. 

more rapid therefore is the change the greater is the com¬ 
bustion, and of course, the greater is the heat. Hence comes 
the increased heat of exercise. Exercise makes more wear 
and tear, and so disengages in the waste more carbon and 
hydrogen to unite with the increased amount of oxygen that 
comes in the quickly flowing blood to the capillaries ; and 
just as in combustion that is attended with flame, the great¬ 
er the amount of fuel the greater is the heat. We have a 
familiar example of the production of heat by exciting the 
circulation, in the expedient often resorted to by laborers 
for warming the hands, of striking them with a swinging 
motion upon the shoulders. 

638. The amount of heat produced in the body depends 
also on the quality of the blood. The richer it is, the more 
oxygen it contains, and therefore, the brisker is the fire in 
the capillaries, and the greater is the heat. You see then why 
it is that those who have a good state of the blood, and ex¬ 
ercise much, maintain the heat of the system better, and so 
need less clothing than those whose blood is weak, and who 
exercise but little. 

639. The heat of the body is maintained in all temperatures 
of the atmosphere very nearly at 98° Fahrenheit. This is, 
you observe, much above even the highest temperature that 
is agreeable to us. You see then that it is essential to the 
comfort of the body that it be giving off heat continually to 
the surrounding atmosphere. If the atmosphere be at 98°, 
the same temperature with the body, there is great discom¬ 
fort, from the fact that the heat is given off too slowly. It 
would not be parted with at all if the skin were not an ac¬ 
tive organ. It is by the evaporation of the perspiration 
thrown off by the skin that the extra heat is got rid of when 
the air is so hot. The temperature in which the body is 
generally most comfortable is about 70°. When the atmos¬ 
phere goes below this, we need the ordinary expedients to 
prevent a too rapid escape of the heat from the body. The 
clothing and the heated air, with which we surround our¬ 
selves to guard against the cold, do not act by communica¬ 
ting heat to the body, but simply by retarding its escape. 

640. Cold is a depressing agent, and exerts as such much 
influence in the production of disease. Statistics show this 
in a striking manner. The statistics of London, for example, 
prove that the mortality of a severe winter is much greater 
than that of a mild one. And this difference is found to be 





HYGIENE. 399 

Means of guarding against cold. Principles to be observed in using them. 


chiefly among the very young and the very old, because in 
them the power of generating heat is feebler than in other 
classes. The greater is this heat-producing power in the 
system, the better does the system resist the depressing in¬ 
fluence of cold. All those means, therefore, which ‘promote 
the vigor of the body, are the best of the safeguards to be used 
against this productive cause of disease and death. But, 
besides thus fortifying the body internally against this 
depressing agent, we have the means of outer defence alluded 
to in § 639, clothing and heated air. As there are many 
errors committed in using these, they require a more parti¬ 
cular notice. 

641. Clothing serves, as I have before said, to shut in 
partially the heat which is generated in the body. Its 
amount and character should be regulated by two circum¬ 
stances—the degree of the cold, and the amount of heat-gen¬ 
erating power in the system. The vigorous require less 
clothing than the weak, because they have more of this power; 
so, also, the body needs less clothing when it is in exercise 
than when it is in a state of rest, because in exercise it gene¬ 
rates more heat. And the same principles apply to heated 
air , for this is an outer covering for the body, interposed 
between it and the cold, like clothing, for the purpose of 
preventing the too rapid escape of the heat generated 
within. 

642. These plain principles are violated in various ways. 
Many, from carelessness or from mistaken notions, are often 
unnecessarily exposed to the depressing influence of cold. 
They are not sufficiently aware of the necessity of guarding 
so much more thoroughly against the cold 'when at rest than 
when exercising. And then, on the other hand, they add to 
the .effect by having too much clothing when in action, or when 
in a warm place. When they thus suffer first from too 
much heat, an after exposure to cold is exceedingly inju¬ 
rious. The weak especially suffer from exposure to cold 
when the body is at rest, and therefore, they should take 
special pains to guard themselves against this depressing 
agent. Any attempt on their part to harden themselves, as it 
is expressed, by making use of as little clothing as the vigor¬ 
ous wear, particularly when the body is in a state of inaction, 
always does harm. The very thin coverings so commonly 
seen on the feet of delicate females are palpably inconsistent 
with this rale of hygiene, and are in ridiculous contrast with 




400 


HUMAN PHYSIOLOGY. 


Cold sometimes a stimulant. Conditions on which reaction depends. 

the stout coverings considered necessary for the feet of 
vigorous men. Various opinions have been expressed in 
regard to the warming of houses, so much in vogue at the 
present day. On the principles developed above, this ex¬ 
pedient for comfort is favorable to health if it be judiciously 
managed, for when the body is at rest, as it commonly is in¬ 
doors, an exposure to cold is depressing, that is debilitating 
to the vital powers. Many other points might be noticed 
in the application of the general principles mentioned, but 
these will suffice. 

643. The depressing influence of cold sometimes produces 
a marked immediate effect. But this is not generally the 
case. Commonly no harm is apparently done at the time, 
and so little is thought of it. But if this influence be con¬ 
tinued day after day, its effects accumulate and become estab¬ 
lished. The vigor of the system is more or less destroyed, 
and some local disease may make its appearance. The 
debilitating influence of cold is in this way a fruitful cause 
of disease, not only in the abodes of poverty, but even 
among those who have ample means of guarding against it. 

644. Although cold is generally a depressing agent, it is 
often indirectly a stimulating one. It is so when, in conse¬ 
quence of its impression upon the skin, it excites what is 
termed a reaction. Several circumstances are necessary to 
this result. 1. There must be the power of reaction in the 
system. There may be so much debility that reaction can¬ 
not be awakened. 2. If the system be in a state of rest, the 
application of cold must be temporary. A continuous 
application of it would be depressing, and would forbid reac¬ 
tion. 3. In an active state of the body, reaction may be pro¬ 
duced even when the application is continuous. Thus the 
mere exercise of dressing may suffice to awaken reaction in 
a degree of temperature which would chill one through if he 
were sitting still. 

645. The system may be accustomed to react under the 
impression of cold in two ways. 1. By exercise in the 
open air in cold weather. Those who have but little out¬ 
door exercise in cold weather, have but little power of re¬ 
action, and therefore feel the depressing influence of the cold 
whenever they are exposed to it. 2. By a judicious use 
of cold bathing. The object of cold bathing, aside from 
purposes of cleanliness, is to accustom the system to react 
under the influence of cold. It is only when reaction occurs 






HYGIENE. 


401 


Cold bathing. To be used variously in different cases. 

under its use that it does good. It does positive harm when 
reaction does not occur; and the harm done in this way 
day after day, by depressing the vital powers, is sometimes 
at length ruinous to the health. 

646. There is a want of proper discrimination in many 
writers on hygiene in regard to cold bathing. It is a mis¬ 
taken ultraism to say, as is often said, that the preserva¬ 
tion of health requires that the whole body should be bathed 
every day in cold water. Neither cleanliness nor the other 
purpose that I have mentioned ordinarily requires so frequent 
and thorough bathing as this. The water may be applied 
to only a part of the body at a time, and yet accomplish all 
that we wish. Indeed, some persons of delicate constitution 
cannot bathe the whole surface at once with cold water. 
They may at first be able to apply it to only a small part of 
the body. But they may, with the aid of friction, after a 
while come to apply it over a considerable portion of the 
surface, or perhaps over the whole. In some persons this 
extension of the limits of the bathing from day to day must 
be done very cautiously ; and there is occasionally one that 
cannot bear it at all over any considerable extent of surface. 
It is necessary for some, in accustoming themselves to cold 
bathing, to begin with using tepid water, making it from 
day to day a little colder. 

647. The best time for cold bathing is commonly in the 
latter part of the forenoon, for the system is then in its 
most vigorous state, and is therefore best prepared to re¬ 
act. But in most persons reaction can be secured at the 
hour of rising, and this is the most convenient time for 
bathing. Few can use the cold bath with profit in the latter 
part of the day, for the powers of the system are then more 
or less exhausted, and full reaction is not easy. The sooth¬ 
ing influence of the warm bath is appropriate at that time. 
There are many other points in regard to bathing that might 
be noticed, but my limits will not permit it. 

648. Thus far I have spoken mostly of the hygiene of the 
body as a structure . But digestion, the circulation, &c, are 
engaged in constructing and repairing organs for the use of 
the mind. In this use, there is wear and tear, and hence is 
the necessity of seasons of rest, that the needed daily repair 
of the organs may be effectually done. The mind uses the 
muscles and bones for motion, the various organs of the 
senses in gaining a knowledge of the world around, and the 

34* 






402 


HUMAN PHYSIOLOGY. 


Exercise necessary to the development of both the muscles and the other organs. 

brain in thinking, willing and designing. Any of these 
organs may be overworked, and after a certain amount of 
work has been done, there needs to be an interval of rest 
for repair. The repair is going on continually, while the 
organs are at work ; but it cannot be done thoroughly with¬ 
out these intervals of rest. Most of the repairing is done 
in these periods. This simple statement suggests the prin¬ 
ciples of hygiene in regard to the uses which the mind 
makes of the organs of the body. These I propose now to 
develop briefly in regard to the muscles, the senses, and 
lastly the brain. 

649. There is a certain amount of muscular exercise 
which is essential to firm health. While no one can fall 
below this amount without impairing the healthy vigor, the 
laborer goes much beyond it without injury. There is a 
wide range, therefore, in the amounts of muscular exertion 
that are consistent with health. 

650. The exercise of the muscles is necessary to their full 
development. When a limb fails to be used, as for exam¬ 
ple in palsy, the muscles become small and lose their firmness. 
When, on the other hand, the muscles of any part of the 
body are much used, they become more developed than the 
other muscles. For example, the labor of the blacksmith 
develops the muscles of his arms largely. The same thing 
is true of the muscles of the leg in the rope-dancer. It is 
only a general exercise of all the muscles of the body that 
develops them in all parts of the frame in their due propor¬ 
tion. 

651. But muscular exercise is also necessary to the pro¬ 
per development of the other textures as well as the muscles. 

I have already remarked upon this in another connection 
(§ 630), and shall not dwell upon it here. There is, however, 
one illustration of this influence of exercise which deserves a 
particular notice. 1 refer to its influence in preventing de¬ 
formity. In the universal vigor and firmness of the textures 
which free exercise tends to produce, there is ordinarily a 
precise equality between the two halves of the body : the 
muscles on the two sides act with equal power; the spinal 
column, the grand pillar of the trunk, is held between the 
muscles that bind its twenty-four bones together with great 
exactness, and there is a beautiful symmetry in the whole 
frame. But w r hen, from lack of exercise, there is want of 
firmness in the textures, this symmetry is apt to be lost 




HYGIENE. 


403 


Deformity of the spine—why more common in females than males 

during the development of the frame, and the spinal column 
is especially apt to become deformed. 

652. There are two immediate causes of this deformity, 
viz.:—irregular muscular action, and irregular pressure. 
Weakened muscles are prone to act irregularly ; and struc¬ 
tures that have lost their firmness, readily yield to any 
pressure that is laid upon them. When there is firmness of 
texture, irregularities of pressure are not apt to produce de¬ 
formity, because the elasticity prevents the permanent in¬ 
fluence of such pressure, The moment the pressure ceases, 
the elasticity of the part restores it to its usual shape. The 
firm regular action of the muscles also tends to the same 
result. Thus, in the case of the spinal column, if the 
posture of the body be such that it is bent over to one side 
for some time, the moment that the posture is altered, the 
elastic cartilages resu*me their usual shape which has been 
temporarily changed by the unusual pressure, and the mus¬ 
cles also that lie along this pillar of bones bring them at 
once to their right position. But if the cartilages have lost 
in some measure their elasticity and the muscles are weak, 
this righting up of the spinal column is not fully accomplish¬ 
ed ; and a succession of slight failures in this respect will 
after awhile, produce a permanent deformity in the direction 
of the most commonly assumed posture. 

653. You can see all this exemplified if you observe the 
difference between males and females in regard to deformity 
of the spine. This deformity is exceedingly common among 
girls, while it is rare among lads. The simple reason is, that 
lads have the invigorating influence of free out-door exercise. 
Too much influence is attributed to posture in producing this 
deformity. Posture is often spoken of as being the chief 
cause of it, and this view of the subject is illustrated exten¬ 
sively with cuts, showing how the deformity is occasioned. If 
this were the correct vie^, there should be much less deform¬ 
ity among girls than among boys in our schools, for the form¬ 
er sit in a crooked posture much less than the latter do. 
So far as posture does have an influence, it is quite clear that 
the prim, fixed posture enjoined upon the girl has a tendency 
to produce deformity, by adding to one of the causes from 
which it proceeds, viz., the weakness of the muscles. A fixed 
uniform posture wearies the muscles, but variations of posture 
relieve them, and so prevent an exhaustion of their power. 

654. The muscles of the back in the female are not only 







404 


HUMAN PHYSIOLOGY. 


Exercise should be varied and general. Gymnastics and Calisthenios, 

weakened in common with the other muscles by a want of 
stirring out-door exercise, but there is a special cause of 
weakness in their case. The tight dress of the girl prevents 
these muscles from having that free action which the loose 
dress of the boy permits. You can see this in the difference 
of movement in the two cases. In the boy, the spine is bent 
and twisted in all directions freely ; but in the girl, both 
custom and the stiff tightness of the dress require a move¬ 
ment almost as if the spine were a single bone, instead of 
being made up of twenty-four bones. The muscles in her 
back, therefore, lose their power and fulness just as the un¬ 
used muscles of a palsied limb do. 

655. Variety should be aimed at in the action of the mus¬ 
cles. A continuous action of any set of muscles is weari¬ 
some and painful. This is well exemplified in the punish¬ 
ment once much in vogue in schools, of making the of¬ 
fender hold a book out at arm’s length for some time. In 
the management of the muscles of the voice, the weariness 
caused by continued sameness of action is often experienced. 
The monotonous speaker or reader tires out these muscles 
much sooner than one who has great variety in his tones. 
For remarks on this and some other kindred points, I refer 
you to §§ 382 and 383. 

656. A general exercise of all the muscles is essential 
both to symmetrical muscular development, and to the full 
attainment of the invigorating effects of exercise. Gymnas¬ 
tics and calisthenics, so called, are considered to be particu¬ 
larly beneficial in this respect. This is true of them; and 
yet they are no better than any other exercises that are so 
varied as to bring the muscles generally into action. The 
varied exercises of walking, running, leaping, riding on horse¬ 
back, dancing, and active sports, are quite as good. And so 
also are the varied labors of the garden, if they be pursued 
with interest and pleasure. There is no especial benefit 
in the extreme variety of exercise sometimes aimed at in 
gymnastics. Variety that is sufficient to bring into general 
action the muscles of the body is all that is requisite. 

657. Gymnastics and calisthenics should always be con¬ 
sidered as subsidiary to the common exercises that I have 
mentioned, and should never be permitted to exclude them. 
When they are made to do this, a temporary benefit is reap¬ 
ed at the expense of a permanent injury. For after the 
novelty of the round of exercises has passed away, they 






HYGIENE. 


405 


Effect of too severe exercise. Hygiene of the Seanses. 

are given up, and the common and now despised exercises 
are not apt to be resumed. Habits of inaction, therefore, are 
often confirmed, instead of being removed, by a systematic 
course of exercises under the high-sounding names of gym 
nasties and calisthenics. 

658. It is necessary that some of the exercise taken should 
be such as to excite strongly the circulation. This I have 
already remarked upon. Exercise should also be taken 
daily. It should be habitual, and not occasional. The habits 
of the English are much better than those of the Americans 
in this respect. It is no uncommon thing for English ladies 
to walk off on excursions of such length, that American 
ladies could not possibly accompany them unless they rode. 

659. But there may be too much exercise. The toil of 
the laborer may be so severe and long continued, that the 
reparative process in the intervals of rest is not competent 
to effect a full repair of the muscles. A gradual exhaustion 
of their power therefore results. Much harm is thus often 
done by severe unremitting toil. Especially is this the 
case when the excess of toil is exacted during the period of 
growth, as it often is among the laboring poor. 

660. It is necessary that exercise should be agreeable in 
order to produce its best effect on the system, on account of 
the genial excitement which then accompanies it. For this 
reason exercise should commonly not be solitary, and there 
should, if possible, be some object connected with it. If the 
observation of nature were made from the beginning of edu¬ 
cation as prominent as I claim in my Preface that it should 
be, there would be no lack of objects in the rambles in 
field and forest taken both for health and the pursuit of 
science. 

661. What has been said of the muscles may be substan¬ 
tially said of the organs of the senses. They require inter¬ 
vals of rest for thoroughrepair. And they may be so over¬ 
worked that complete reparation may be impossible, and so 
their pow T er may be gradually exhausted. The office of the 
senses is to receive impressions from things around. What¬ 
ever gives an impression to any organ of sense may be re¬ 
garded as a stimulus to it. If the stimulus be too great 
or too long continued, injury is done. This is very obvious 
in regard to the eyes. They are often injured by too much 
light.° A word of caution is needed in regard to the produc¬ 
tion of near-sightedness. This is often caused in students 
and others by holding objects too near the eyes. 






406 


HUMAN PHYSIOLOGY. 


Necessity of seasons of rest to the hrain. Overworking the brain. 

662. I come now to the hygiene of the brain. This is the 
great central organ or instrument of the mind, by which it 
receives the impressions made upon the senses, compares 
and arranges the knowledge thus gathered, and originates 
those impressions that are made by it upon the world 
around through the action of muscles. It is a very com¬ 
pound instrument. It needs, like the muscles, seasons of 
rest for the full repair of the wear and tear occasioned in its 
daily use. It may be overworked, and then the repair will 
not be complete, and gradual exhaustion of its powers will 
result, occasioning disease in some form. A significant illus¬ 
tration of the importance of seasons of rest for repair in the 
case of the brain is furnished in the fact, that insanity is not 
apt to result from mental disturbance, unless the subject of 
it fail to have his regular sleep. If he sleeps well, the work 
of repair is so well done in the brain in its nightly seasons 
of rest, that the disease, which might otherwise occur, is 
prevented. 

663. With proper intervals of rest, the mind can perform 
a large amount of labor without injury to the brain and ner 
vous system, it there be no undue excitement, and no wor 
rying and depressing anxiety. This is shown in the length 
ot life that so often accompanies the quiet but laborious 
pursuits of science. While, on the other hand, the excite¬ 
ment and anxiety of a life of business, especially as it is 
ordinarily pursued in this country, it is well known, is not 
favorable to longevity. 

664. It is especially important that the brain should not 
be overworked during the period of its growth. The reason 
is the same as that which we have for the caution, so univer¬ 
sally observed, in regard to putting too much labor upon 
the muscles of a young horse. And $et there is buoyant 
activity in the child, which is disposed to show itself in the 
operations of the brain as readily as in the action of the 
muscles. If this activity be turned into proper channels, 
and be not too much stimulated, no injury will be done to 
the delicate textures of the brain. 

665. Although much is said of the danger of over-stimu¬ 
lating the brain of the child, the difficulty does not so much 
lie here, as in the manner in which the mind is led to act. 
There is commonly too much of mere drudgery, and of 
storing the mind with unintelligible, and therefore uninter¬ 
esting matters. The mind, accordingly, is dissatisfied and 




HYGIENE. 


407 


Influence of quiet cheerfulness. The passions. Alcoholic stimulants. 

wearied. The tedium of the labor exhausts, and so the 
brain is essentially impaired. When early education shall 
become in all respects what it ought to be, greater real ac¬ 
quisitions will be made than we witness now, without any 
injury to the growing brain. 

666. It is well known that undue mental excitement and 
the depression of anxiety are together apt to produce insanity. 
Though they generally stop short of this result, they always 
injure the health and shorten life. A firm and cheerful mind 
is favorable to longevity, but the anxious and fretting are 
seldom, if ever, long-lived. 

667. As the passions must have much influence upon the 
action of the mind, and therefore upon the state of the brain 
and nervous system, the proper regulation of them is essen¬ 
tial to health and longevity. Much of the positive disease 
of the brain, and of the general nervous derangement so 
common among the educated and refined, comes from the 
bad management of the passions. 1 cannot dwell upon this 
point, but remark, in passing, that the fictitious literature 
of the present day exerts a considerable influence in this 
way. 

668. There are certain articles in common use in the 
community, which produce so deleterious an influence upon 
the system, that they demand a more extended notice than 1 
can give them in this chapter. I refer to alcohol and 
tobacco. They act chiefly upon the brain and nervous 
system, the former as a stimulant, and the latter as a seda¬ 
tive. The use of opium is so limited compared with these 
that I shall not dwell upon it, especially as it is never de¬ 
fended. 

669. No fact is more thoroughly demonstrated than that 
the system has no need of alcoholic slimulants while it is in 
a state of health. So far then as we look at mere necessity, 
these articles are to be considered simply as medicines, re¬ 
quired only in diseased conditions. But it is said by some 
that they can be used in small quantities without injury to 
health. This cannot be claimed with any shadow of reason, 
unless in relation to very small quantities. Entire absti¬ 
nence is at least safe, and there are so many other things 
supplied by a bounteous Providence to gratify the taste and 
the appetite, that we can easily forego the use of alcoholic 
stimulants; and we ought to be willing to do so, if the good 
of others require it. The common use of these articles as 




408 


HUMAN PHYSIOLOGY. 


Tobacco an active poison. Coffee and Tea—the propriety of their use not settlod. 

beverages is one of the most prolific of the sources of disease; 
and it is a significant fact, that the very moderate use, claim¬ 
ed by some to be innocuous, has a strong tendency to pass 
into a larger use, even so large that its deleterious influence 
upon health is palpable. 

670. The evidence is quite as clear in relation to the inju¬ 
rious effects of tobacco. This has sometimes been erroneous¬ 
ly termed a stimulant. The error arises from the well- 
known discomfort of the habitual user of it when he is depri¬ 
ved of the use of this drug. This discomfort has a depress¬ 
ing influence, and when his system is brought again under 
the influence of tobacco the depression is removed, not by 
any direct stimulating effect, but by the relief given to the 
uncomfortable sensations. Tobacco is really one of the 
purest sedatives we have. It depresses vital action. It acts 
chiefly upon the nervous system, and therefore, has a strong 
tendency to produce nervous diseases. While it is injurious 
to all, it is especially so to those who have a low vital action, 
and are disposed to nervous complaints. 

671. Tobacco is so active a poison that extreme caution 
is required whenever it is administered, as it sometimes is, 
as a medicine. The effects of even a small amount of it upon 
one that is unaccustomed to its use are of the most decisive 
character. And that must be an exceedingly artificial con¬ 
dition of the system, in which, by continued use of this drug, 
large amounts come to be borne with little apparent effect. 
The evidence of the deleterious influence of tobacco upon the 
system is as unequivocal as that which we have in regard to 
the influence of opium, and wonderfully strong is that sla¬ 
very to appetite that makes one persist in the use of this drug 
in spite of such evidence. 

672. Coffee and tea are often included in the same cate¬ 
gory with alcohol and tobacco. Granting all that is claimed 
in regard to the injurious effects of these articles, it is pre¬ 
posterous to class them with such poisons. The evidence in 
regard to them is conflicting, and all that is settled as yet is, 
that in some persons they exert a bad influence upon the 
nervous system. If this should be found to be true of a 
very large proportion of all who use them, the evidence 
would be conclusive against the propriety of their use as 
common beverages. But as yet this has by no means been 
proved to be true. 

673. There are certain noisonous emanations, to which 





HYGIENE. 


409 


Poisonous emanations. General view of the causes of disease. 

the human system is often subjected, that are largely de¬ 
structive of health and life. They arise from decomposing 
filth of various kinds. Besides predisposing the system to 
the action of contagious and epidemic causes of disease, they 
also of themselves create disease. It is these emanations 
that render the close air of a crowded city, especially in its 
narrow lanes, so impure and fairly poisonous. And this 
impurity of the air is one of the chief causes of the difference 
in disease and mortality between the city and the country. 
The difference is greater than is generally supposed. It has 
been found by statistics in England, that there are 24 per 
cent, more deaths from consumption, and 55 per cent, more 
deaths from typhus, in cities than in the rural districts, and 
the mortality from the diseases of childhood is twice as great 
in the city as in the country. In what way these emanations 
act we know not. But, although much is to be attributed 
to a mere want of ventilation, that is, to a lack of oxygen, 
there is no question that these emanations often act as posi¬ 
tive poisons to the system. 

674. In developing the principles of hygiene, I have 
noticed many of the prominent causes of ill health and dis¬ 
ease. They are chiefly these: 1. A disregard in various 
ways of the rules relating to the digestive process. 2. Com¬ 
pression of the chest, especially during the period of growth. 
3. Deficiency in the supply of pure air to the lungs. 4. Fail¬ 
ure to guard properly against the influence of cold and 
heat, chiefly the former. 5. A lack of active exercise in the 
open air. 6. Overworking the muscles. 7. Errors in the 
management of the moral and intellectual powers. 8. The 
influence of such articles as alcohol and tobacco. 9. Emana¬ 
tions from decomposing filth. It is well thus to look at 
these causes grouped together, endeavoring to give to each 
its due prominence. For various and exclusive views are 
often taken of this subject. Quite commonly some of these 
causes are kept entirely out of view, while others are strong¬ 
ly pressed upon our attention. Disease is generally a very 
compound result , produced by a concurrence of several of 
these causes, and sometimes even of all of them. 

675. These causes of disease, it will be observed, are more 
or less under our control. Some of them are entirely so. 
A knowledge of their operation, and an earnest endeavor to 
remove them, would, therefore, vastly diminish the amount 
of ill health and disease. 


35 




410 


HUMAN PHYSIOLOGY. 


Our control over the causes of disease. Preventive and curative measures 

67G. It is true that there are some other causes of disease, 
of which we know but little, and over which we have little or 
no control. Such are the causes of various contagious and 
epidemic diseases. But these really produce a much less 
amount of disease than the causes which I have mentioned. 
Their action is occasional, and confined to localities; not 
continual, and in all places. And besides, they may to a 
great extent be shorn of their power, by guarding against 
those causes of disease which are more or less under our 
control. It is those who neglect to do this that commonly 
become most readily the victims of contagions and epide¬ 
mics. 

677. There is much interest in the community in regard 
to the cure of disease, but there is a blind indifference to its 
prevention. And yet vastly more can be done in the diminu¬ 
tion of disease by preventive than by curative measures. The 
ravages of consumption, for example, can undoubtedly be 
greatly lessened by preventing the operation of its principal 
causes ; and yet what is said about these causes is little 
heeded, and the public attention is engrossed with the 
delusions of consumption-curers. It is emphatically true 
of this malady, that multitudes more can be saved by 
preventive measures than by curative ones. Against no 
disease can hygiene achieve greater victories than this. 
The neglect to use preventive measures against this and 
other diseases arises chiefly from an ignorance of the prin¬ 
ciples on which these measures are based. The prevalent 
indifference, therefore, on this subject can never be fully re¬ 
moved, till the general introduction of Physiology as a study 
into our schools shall make these principles familiar to the 
mass of the community. 




APPENDIX: 


CONTAINING 

DIRECTIONS TO TEACHERS FOR THE USE OF THE BOOK, 
AND QUESTIONS. 


In order to be able to teach from this book properly, the teacher should 
himself study all of it thoroughly before he begins his instruction. If 
he merely keep a little in advance of his class, he will fail in his concep¬ 
tions of the general scope and plan of the book. If the interest of the 
subject awaken in him and in his pupils a spirit of inquiry, there will 
be a continual looking forward to points which are explained and illus¬ 
trated further on in the book. Now if the teacher has made himself 
master of all the subjects treated of, instead of turning off the inquiry 
of a scholar without an answer, or even the promise of an answer in the 
future, or endeavoring to clear up the points about which inquiry is 
made, which of course he can do, under the circumstances, in an imper¬ 
fect manner at the best, he can satisfy the scholar by informing him that 
these points will be found explained in their proper place at a future 
stage of the investigation. I have aimed to have every topic treated of 
in its right place in the development of the general subject, and the 
teacher should be thoroughly master of the whole book at the outset, in 
order that he may fully carry out my plan in the mode of developing the 
topics to the minds of his pupils. 

It must be obvious to any teacher that he can teach the minutiae of 
the subject with more of interest, to say nothing of thoroughness, if, 
while doing it, he takes in the general views presented, and has in mind 
the relations of the particular topics in hand to other branches of the 
subject. Indeed it will be profitcfble occasionally for the teacher to 
afford the scholar some glimpses of the interesting fields to be explored 
further on, taking care, however, not to anticipate so much, as to mar the 
natural method and order of developing the whole subject, which I have 
taken such especial care to observe in the preparation of the work. 

The teacher should read the book through in course. If, instead of 
doing this, he opens to some chapter in the middle or latter part of the 
book, he may get the impression that too high matters are treated of, 
and that the minds of his pupils are not competent to understand them. 

* They cannot be understood unless there be a preparation of mind for 
them ; and just this preparation is aimed at ii; the first part of the 
hook. And besides, it is quite important that the subjects treatM of 



412 


APPENDIX. 


should be developed to the mind of the teacher in the same order m 
which they are to be developed to the minds of his pupils. 

In the engravings clearness has been aimed at rather than beauty. 
Yet I should not do the engraver justice if I did not say, that in beauty 
they are generally quite equal to those which we find in our standard 
professional works on physiology. It is to be borne in mind that wood* 
cuts cannot represent correctly the beauty and delicacy of living struc* 
tures. These can be realized only by seeing the structures themselves. 
Another thing to be kept in mind is, that parts which are represented in 
engravings with definite lines for the sake of distinctness, are ordinarily 
not thus distinct in the structures. To make them so, the dissecting- 
knife must separate them, and take off the cellular substance, which, as 
the general packing material of the body, everywhere connects adjacent 
parts together. 

The teacher can be aided very much in givftig his scholars a correct 
idea of different organs, by presenting to them organs taken from the 
bodies of animals. Thus, in giving them an idea of the lungs, the 
lungs of a calf or a sheep can be used. A pipe may be fastened into 
the windpipe ; and by blowing into this, you can show how the lungs are 
inflated. An idea of the appearance of the human brain can be given by 
means of the brain of a calf, or any other animal of sufficient size. 
An ox’s heart may be used in showing the structure and arrangement 
of the valves and other parts of that organ, for they are essentially the 
same as in man. A very good idea of the arrangement of the cartilages 
that make up the larynx, can be obtained from the larynx of an ox or 
cow. The general shape and arrangement are the same as in man. It 
is some trouble to clear the parts of muscular substance, but the teacher 
can get some physician or medical student to do it for him. When the 
preparation is once made, it can be dried for permanent use. I have one 
which I made twenty-five years ago. In drying, it will be necessary to 
keep the wings of the thyroid cartilage apart by a wedge, and the 
supple epiglottis must be placed in such a position as not to interfere 
with a view of the interior of the larynx. The large eye of the ox can 
be made use of to show the various parts of that organ, and also to 
show the formation of the images of objects on the retina. 

One great advantage of thus using parts from different animals is, 
that a taste is given for the examination of the phenomena of life, with 
its wonderful mechanisms, wherever they may be seen. All living na¬ 
ture thus becomes full of suggestive interest to the young student. 

There are some things of which plates can give no correct idea. 
Such, for example, is the cellular membrane. The attempt to represent 
it is made in most books on physiology, but it is an entire failure. 
I have a plate representing its cells as seen in a dried preparation under 
the microscope ; but to give the scholar an idea of it as it appears to the 
naked eye in its natural condition, I refer him to it as seen in any com¬ 
mon piece of meat between the muscles and between the fibres of each 
muscle. The teacher can use a piece of meat for this purpose. The 
difference between muscles, tendons, and ligaments can be shown in the 
same way. 

Those figures which are mere diagrams it will be well for the scholar 
to draw on the blackboard, and his skill in description and remark may 
be exercised for his own benefit and for that of the class. He slioulo 



APPENDIX. 


413 


be trained in this exercise in such a way, that he will acquire the power 
of giving well-proportioned and well-arranged descriptions, without the 
aid of prompting by minute questions from the teacher. 

It will be proper to say something of the use which should be made 
of the questions that I have prepared. I have two reasons for not 
placing them at the foot of the page. One reason is, that the book 
is designed for general reading as well as for instruction. But the 
chief reason is, that I wish to prevent a too free use of questions on the 
part both of teacher and scholar. The marking with the pencil of parts 
which contain the answers to the questions, so often done in our 
schools, should never be permitted by the teacher, for reasons that I 
need not stop to notice. 

The scholar should read the text at first without reference to *he 
questions ; and then the questions can be made use of, perhaps with 
profit, to fix definitely in the mind the principal points that are brought 
out. It will be a useful exercise for the scholar, after reading a page or 
two, to think over the main points, and then see by the aid of the ques¬ 
tions whether any important point has escaped his recollection, or failed 
to make the proper impression on his mind. 

The questions that I have constructed will, I think, be found to be 
fitted to the great majority of scholars. But of course the teacher will 
vary them to suit the different capacities and mental attitudes which he 
finds in his class. 

It is best not to have an uniform mode of asking questions, even with 
the same scholar. Variety should be given to the mode of hearing the 
recitation. Sometimes the questions should be minute, and at other 
times the mind of the scholar should be left to go on with as little lead¬ 
ing as possible. 

The scholar should be encouraged occasionally to give the substance 
of a whole paragraph, or even of more than this. In doing so, any 
failure in arrangement or proportion can be noticed by the teachei-, for 
the benefit not only of the scholar that is reciting, but also of the whole 
class. The general scope of an argument may also be given in the 
same way, and the manner of doing it be made the subject of criticism. 

The numbers attached to the questions refer to the pages, this being 
more convenient to the scholar than a numbering by paragraphs wujid 
be, though of course it cannot be quite as definite in all cases. 

35 * 



414 


APPENDIX. 


QUESTIONS. 


CHAPTER I. 

13. In what respect are a crystal and a plant alike! How' do they 
differ in the modes of their formation ! What different offices do the 
organs in a plant perform! What is meant when we call the plant an 
organized substance, and the crystal an unorganized substance! 

14. Do the organs in the plant act wholly on mechanical principles ! 
Or on chemical ? What principles control the mechanical and the che¬ 
mical 1 What two classes are there of organized living beings! How 
do they differ as to the complex character of their organization! Under 
what two grand divisions do you class all the substances of the mate¬ 
rial world! How do plants and animals differ from minerals as to the 
parts of which they are composed! 

15. What is assimilation! Explain it as it takes place:—First, in 
the plant, and secondly, in the animal. How do organized and unor¬ 
ganized substances differ as to permanency! Point out the mode and 
the extent of the change that occurs in the organized. 

16. Why is there more change in animals than in plants! How 
can minerals be changed! Are they productive, as animals and plants 
are! Contrast organized and unorganized substances in regard to 
change in the phenomena that you see in the world around you. 

17. How do organized and unorganized substances differ as to regu¬ 
larity in form! What does irregularity in the unorganized arise from ! 
How does the law of regularity operate in organized substances! 
Does the exactness which it sometimes shows appear in straight or in 
curved lines! 

18. In which is the regularity the most wonderful, the organized or 
*he unorganized, and why! Give the four reasons assigned :—First, as 
to change; secondly, as to variety of form ; thirdly, as to its continu¬ 
ance from age to age ; and fourthly, as to its preservation in the midst 
of a certain range of irregularity. 

19. Exemplify the last point by reference to the human countenance. 
How is the law of regularity exemplified in the two halves of the body! 
Mention some organs which are destitute of this symmetry; mention 
also some animals that do not exhibit it. What is the distinction 
between organized and unorganized substances as to limit of size 1 

20. How do organized and unorganized substances differ as to their 
structure! How do they differ as to the number of elements of which 
they are composed! What are the four principal elements of organ 




APPENDIX. 


415 


t 


ized bodies 1 Which one of these is solid 1 In what fonn are the other 
three "? How many elementary substances are there in the material 
world \ How many of these are found in plants and animals ] 

CHAPTER II. 

21. Point out the difference between the plant and the animal as to 
locomotion. How does this difference make it necessary that the ani¬ 
mal should have a stomach 1 Trace the analogy between the stomach 
in the animal and the roots in the plant. What is the difference 
between most animals and plants as to central organs "? What is their 
difference as to the effect of mutilation upon them 1 

22. What is the distinction between animals and vegetables as to sen¬ 
sation and spontaneous motion 1 Have all animals consciousness and 
thought 1 Name some exceptions to the distinction as to locomotion. 
What is the difference between the motions of such plants as the sensi¬ 
tive-plant and catch-fly, and those of animals "! Make the comparison in 
relation to the hydra, which describe. 

23. Can the distinction as to a digestive cavity always be made out "? 
If it could be, should it be considered an essential distinction 1 What is 
the really essential distinction between animals and plants 1 What part 
of the structure of animals is peculiar to them 1 Has this structure 
ever been discovered in any plant"! Why ought we to be able to dis¬ 
cover it in the sensitive-plant and catch-fly, if it were the cause of their 
motions"! 

24. Is the nervous system necessary to the carrying on of nutrition ? 
What are the functions of organic life "? What of animal life "! What 
is the order of action in the nervous system 1 In what respect is this 
order not observed in some cases"? Give some examples of instinctive 
and automatic motion. How does the heart differ from the muscles of 
breathing as to the influence of sensation and of the will on its action 1 

25. What is the office of the central organs of the nervous system 
in sensation and motion 1 In proportion to what is the chief central 
organ, the brain, found developed 1 Describe in general the difference 
in development between the nervous system and the system of nutri¬ 
tion in different animals. Does the nervous system undoubtedly exist 
in those animals in which it cannot be found 1 

26. What reason have we to attribute to such animals the exercise of 
thought, will, and consciousness 1 Illustrate by reference to the Hydra. 

27. What is the distinction between animals and plants as to their 
chemical composition "? In which is carbon the characteristic element, 
and in which is it nitrogen"! From what organs in animals is carbon 
thrown off! In what organs in plants is it absorbed"! 

CHAPTER III. 

27. How is man commonly classed in the animal kingdom"? On 
what ground can the classification be claimed to be correct"! Does this 
classification recognize at all the essential distinctions between man and 
other animals"? What are those distinctions 1 

28. Should the received classification be considered as giving man his 
true position in the scale of being"! What bearing has man’s immor 



416 


APPENDIX. 


tality on this subject! Is the difference between man and other ani¬ 
mals like that which we see between different animals ! Is it a mere 
difference of degree! What notice should the naturalist take of the 
difference 1 

29. What is the distinction made in the common classification 
between man and such animals as apes and monkeys! Can these animals 
oe properly said to have four hands ! How do the hands which they are 
said to have resemble the hand of man, and how do they differ from it! 

30. What is said by Sir Charles Bell about the hand ! What by 
Aristotle, and by Anaxagoras 1 State some particulars in which the 
structure of man differs from that of^the inferior animals. 

31. What relation have the peculiarities of man’s organization to his 
mental peculiarities'! Why is it important that the essential distinc¬ 
tions between man and animals should be prominently taught! What 
is the theory of Robinet! 

32. What is the teaching of a true science in regard to the Creator’s 
agency 1 What is the theory of gradations in nature 1 What are the 
objections fatal to this theory, as stated in $ 491 

33. What are the real gradations in nature! Are these gradations 
in each of the kingdoms regular! Is man inferior to some animals in 
certain endowments! Give some examples. Is it strictly true that 
man is the most perfect of animals! In what respect is there a grada¬ 
tion in the three kingdoms of Nature! Is all Nature wholly tributary 
to man! 

CHAPTER IV. 

35. Of what advantage is it to the student, in studying human physi- 
ology, to observe the analogies in the processes of life between man and 
other living beings or things! What is the difference between Anatomy 
and Physiology! 

36. What functions distinguish animals from plants! Into what two 
classes of subjects is Physiology naturally divided! Remark on the 
wide range of subjects presented in Physiology. In what respect does 
this study differ from all others! 

37. Of what two parts is bone composed! What are the propor¬ 
tions of these parts in childhood—in adult age—and in old age 1 How 
can you obtain these parts separate from each other! What is the 
animal part of bone! What relation does this sustain to the mineral 
part! What is the arrangement of the two parts of bone in the very 
young child! What is true of the skeleton of many fishes! 

38. Mention some cartilages that never have any mineral matter 
deposited in them. With what are the bones joined together! By 
what are they moved! How do muscles act! What is the office of 
the tendons 1 What is their structure 1 What is the most common 
texture or tissue of the body! Why is it called areolar or cellular / 
How can you get the best idea of this texture 1 Mention its different 
uses! 

39. In what portions of the body is this tissue most abundant! In 
what ways does the free communication between the cells of this tissue 
become manifest to us! How is its elasticity affected by dropsy in it! 

40. What are the uses of the fat deposited in the cells of this tissue 1 



APPENDIX. 


417 


What fact is stated in regard to hybemating animals 1 How is the fat 
kept from oozing through the pores of its cells 1 What cavities does 
the mucous tissue line 1 How is the secretion of mucus effected ! What 
is its chief use ! 

41. "What parts of organs are lined by the serous tissue! In what 
important respect do serous membranes differ from mucous ! What is 
the appearance of the serous membranes 1 How is dropsy produced in 
them 1 Are the organs of the body composed of many tissues! Take 
the stomach as an example, and describe its structure. Give a 
summary of the nutritive functions as described in $ 69. 

CHAPTER Y. 

42. Give a summary of the processes of digestion. 

43. Of what substances is the body of a tooth composed, and how 
are they arranged! What are the different shapes of teeth, and for 
what different purposes are they fitted! How do the teeth of carnivor¬ 
ous animals differ from those of the herbivorous! How does the 
motion of the lower jaw differ in the two classes! 

44. What is the shape of the teeth in the insectivorous! What in 
the frugivorous! What is the peculiar arrangement of the enamel in 
the teeth of the herbivorous, and for what purpose! What can be 
inferred about an animal from an examination of his teeth! Why is 
man said to be an omnivorous animal 1 Why are his tearing teeth less 
in length and in power than those of carnivorous animals! 

45. What has the common whale in place of teeth 1 What is the 
purpose of the arrangement! What supplies the place of teeth in 
birds 1 What is the use of the saliva 1 Describe the situation and 
arrangement of the glands that supply this fluid. 

46. How much saliva is secreted by the salivary glands during a 
meal! Why is more saliva than usual needed when one is speaking! 
What effect does motion of the mouth have on the secretion! How 
are these salivary glands affected by tobacco-chewing 1 

47. Explain the influence of sympathy in the secretion of saliva. 
What are the two kinds of fluid secreted by the salivary glands, and 
what is the purpose of each kind 1 Describe the various parts engaged 
in the act of swallowing, as represented in figs. 10 and 11. 

49. Describe the arrangement of muscular fibres in the oesophagus. 

50. What is the character of the gastric juice! By what is it 
formed! Describe the appearance of the mucous membrane of the 
stomach, as seen by Dr. Beaumont, in the case of Alexis St. Martin. 
To what is the amount of gastric juice proportioned! What is the 
effect of stimulating the stomach to too large a secretion of it from day 
to day! What is the nature of its action on the food! How is the 
application of it to all portions of the food secured! 

51. Describe the arrangement of the muscular fibres of the stomach, 
and the manner of their action. What is the chyme! What is the 
arrangement of the valve called the pylorus 1 

52. When is the pylorus especially in action! If there be difficulty 
in digesting the food, what is the effect on the action of this valve! 

53. What are the different theories in regard to the process of diges¬ 
tion ! What is the true character of the process! What is the conso- 

34 



418 


APPENDIX. 


quence if fresh food be introduced into the stomach while the process is 
going on 1 Why is the practice of eating between meals a bad one ? 
Why does eating fast, do harin'? What effect has great variety in 
food ? How does exercise affect digestion ? Relate - the experiment 
with the two dogs, and state what it proves. 

54. What shows that hunger does not arise from emptiness ? What 
that it does not arise from the irritation of the gastric juice? What is 
the cause of hunger? W r hat is the seat of the sensation ? Upon what 
does the degree of hunger depend ? What must be the state of i 
stomach to have this sensation exist ? 

55. How do mental impressions sometimes destroy the sensation ot 
hunger ? How does food remove it so much before any nourishment is 
diffused through the system ? What is the cause of thirst ? Where is 
its seat ? 

57. Describe the arrangement of the digestive organs as seen in fig. 
16. What are the uses of the mesentery? Where are the bile and 
the fluid secreted by the pancreas mingled with the chyme 1 What is 
one of the offices which they execute ? 

58. What is the chyle ? What are the lacteals 1 What glands do 
they enter ? After passing on from these glands, into what duct do they 
empty the chyle ? What is the size of this duct, and where does it 
pour its contents ? 

59. Describe the operation of the suction power at the mouth of 
the thoracic duct. What becomes of the chyle thus forced into the 
blood ? Why is the mucous coat of the intestine full of folds ? 

60. What is the general rule by which the variation in the digestive 
apparatus in different animals is governed ? Exemplify by a compari¬ 
son between herbivorous and carnivorous animals. What is the length 
of the alimentary canal in the lion ? What in the sheep ? What in 
man ? In what animals is the stomach most complicated ? Describe 
the apparatus of digestion in the sheep, and its successive processes. 

62. W T hich of the four cavities in the sheep’s stomach is the real sto¬ 
mach ? Into which cavity does fluid matter always go ? What is the 
arrangement when the animal is suckling? Describe the digestive 
apparatus of birds as exemplified in the turkey. 

63. What circumstances govern the variations of the digestive 
organs in different animals ? What is true of the stomach in the lower 
orders of animals ? What peculiarity is there in the Hydra in regard 
to its stomach ? 

CHAPTER VI. 

64. What are the different parts of the apparatus of the circulation I 
Describe the agency of each in circulating the blood. 

65. What relation does the heart bear to the rest of the circulating 
apparatus ? What is the difference between the arteries and the veins 
in their structure ? What two reasons are there for this difference ? 
What is the pulse 1 

66. How do the arteries and veins differ in the mode of their divi¬ 
sion ? How does the venous system differ from the arterial in capacity ? 
How in regard to rapidity of flow of the blood ? Describe the valves in 
*lie veins. 



APPENDIX. 


419 


67. Why are these valves needed! Why is it more dangerous to 
wound an artery than a vein 1 Give some examples, showing how on 
this account the arteries are seated more deeply than the veins. 

68. W T here are the arteries superficially situated, and why 1 Describe 
the common mode of bleeding from the arm. What is the proper way 
to stop bleeding from an artery 1 

69. What is an aneurism ! When a ligature is tied around the 
artery above an aneurism in a limb, how is the limb to be supplied with 
blood! What is the chief agent in the circulation of the blood 1 How 
can you illustrate the contraction and the dilatation of the heart ! 

70. What phenomena show that the blood-vessels exert an active 
agency in circulating the blood ! How does the circulation through the 
liver show that the capillaries are active agents in circulating the 
blood 1 

71. Why are the veins generally full of blood after death, while the 
arteries arc nearly empty 1 

72. What is the origin of the term artery ! Why do we not in com¬ 
mon language speak of the blood as running in the arteries as well as 
in the veins ! When did Harvey discover the circulation of the blood! 
What is the color of the blood in the arteries! What color has it in 
the veins! Where is it changed from red to purple 1 What other 
changes besides that of color take place! W T hat would be the conse¬ 
quence if the dark venous blood should be sent to the brain 1 

73. Where is the change in the blood from purple to red effected! 
How is the apparatus arranged so as to send the purple blood to the 
lungs to be changed! Explain the diagram showing the plan of the 
two circulations. 

74. What is the difference in the two circulations as to the color of 
the blood in the veins and the arteries! What is the difference between 
the change of the blood in the capillaries of the lungs, and that which 
takes place in the capillaries of the general system ! Describe the parts 
of the right half of the heart as represented in Fig. 26. 

75. Describe the manner in which the auricle and ventricle, with the 
valves, act. Give the illustration as represented in Fig. 27. 

76. What is the difference in size and strength, between the auricle 
and ventricle 1 What is the size of the heart! Describe the arrange¬ 
ment of the valves of the aorta. 

77. Describe the special provision to prevent leaking in these valves. 
How are the walls of the heart supplied with blood 1 

78. Describe the valves between the auricles and the ventricles. 
Why are they regulated by muscles ? 

79. Why are there no valves where the blood pours into the auricle 
from the venae cavae 1 Describe the parts of the heart as represented in 
Fig. 31. 

81. Describe the circulation as given in the map of the heart in 
Fig. 32. 

82. Describe the situation of the heart and its blood-vessels, as repre¬ 
sented in Fig. 33. 

83. How do the four parts of the heart act without disturbance! 
What is the difference between the two sounds of the heart! What is 
the cause of the first sound! What of the second! How is the pulse 
produced! Explain the impulse of the heart against the chest. 



420 


APPENDIX. 


84. Explain the plan of the pericardium. 

85. Has the heart any repose 1 Give some calculations as to the 
Amount of work, it does in a lifetime. 

CHAPTER VII. 

86. What two objects are effected by the respiration 1 Of what are 
the lungs composed ! To what is their spongy lightness owing 1 How 
minute are the air-cells or vesicles !. In what way is the change pro¬ 
duced by the air in them upon the blood 1 

87. Describe the arrangement of the larynx, the trachea, the bronchi, 
and the lungs, as exhibited in Fig. 36. How are the heart and the 
lungs arranged in the chest 1 

88. What is the pleural Why are the lungs not fastened to the 
walls of the chest 1 Describe the manner in which the air is made to 
enter the chest in breathing. Describe the framework of the chest, as 
represented in Fig. 37. How are both lightness and strength secured 
in this structure! 

89. Why are the ribs joined to the breastbone by means of carti¬ 
lages! What is the chief connecting material of this framework! 
What is the diaphragm, and how is it arranged! 

90. How does the diaphragm act 1 Describe inspiration and expira¬ 
tion as illustrated by Figs. 38 and 39. 

92. In what way do other muscles, besides the diaphragm, act in res¬ 
piration ! Describe their arrangement and action, as represented in 
Fig. 40. 

93. What is the arrangement of the muscular fibres between the ribs, 
and their mode of action 1 In what directions are the ribs moved by the 
muscles in the neck and between the ribs ! Do these muscles act much, 
if at all, in ordinary easy respiration! Under what circumstances do 
they act strongly 1 

94. If air were admitted to the outside of the lungs by openings in 
the walls of the chest, what would be the result! How are the blood 
and the air kept from mingling in the lungs, while they are brought so 
near together that the air changes the blood ! What experiment shows 
that blood can be acted upon by air through pores 1 How important is 
the office of the air-cells ! What provisions are made for securing to 
them sufficient room under all circumstances! Illustrate by reference 
to the state of things in violent exercise. 

95. If the expansion of the chest be restrained in any way, what in¬ 
fluence is exerted upon the air-cells! In what two ways does violent 
exercise injure the lungs when the chest cannot be well expanded! 
What is said of the influence of compression of the chest in the pro¬ 
duction of disease in the female sex ! 

96. What is said of the extent to which compression of the chest is 
often carried 1 

97. What is said of the gradual moulding of the chest by continued 
compression during its growth ! How is death produced in drowning! 
How is water prevented from getting into the lungs in any quantity ? 
If arterial blood could be supplied to all the organs while the breathing 
is stopped, what would be the result! What contrivance has the whale 
for this purpose! 



APPENDIX. 


421 


98. What is the arrangement of the gills of a fish 1 By what expe¬ 
riment can you prove that it is the air in the water that acts on the 
blood in the gills, and thus keeps the fish alive 1 Why cannot the fish 
use air that is not mingled with water 1 What provision in the land-crab 
enables him to live in air as well as in water 1 Describe the arrange¬ 
ment of the gills in the lob-worm, and the larva of the May-fly. 

99. How are the respiratory organs arranged in insects 1 What is 
the effect of covering their stigmata with varnish 1 

100. For what two purposes is the apparatus of respiration largely 
developed in birds 1 What special arrangement is there for securing 
lightness 1 

101. By what experiment can you show that carbonic acid is thrown 
off from the lungs 1 What are the components of the air, and what is 
their proportion I Which of these is essential to life 1 Why would it 
not be well to breathe pure oxygen alone 1 Where has it been sup¬ 
posed till recently that the oxygen of the air unites with carbon to make 
carbonic acid 1 Where does this union take place 1 

102. What facts settle the last question 1 Does the change effected 
by the air upon the blood in the lungs take place to some extent, when 
blood drawn from a vein is exposed to air 1 What experiment illus¬ 
trates the manner in which the air acts on the blood in the lungs 1 

103. How much carbon is contained in the carbonic acid thrown off 
from the lungs in twenty-four hours 1 What effect does this gas produce 
upon the health if ventilation be imperfect 1 

104. What becomes of the carbonic acid thrown off from the lungs 
of animals 1 How is the air replenished with oxygen 1 How is the 
equilibrium preserved in different climates 1 What effect has light upon 
the discharge of oxygen from the leaves of plants 1 By what process 
is the heat of the body maintained 1 Trace its analogy to ordinary com¬ 
bustion. 

105. What was formerly supposed in regard to the place of the pro¬ 
duction of animal heat 1 What objection was made to this supposi¬ 
tion 1 Where was it at length discovered that the heat is made ? 
What are the three sources of fuel for keeping up the animal heat 1 
Why is so large a quantity of oily food eaten in cold climates 1 How 
do cold and tropical climates differ in the provisions of nature in this 
respect 1 

106. How is the use of fat in maintaining heat exemplified in hiber¬ 
nating animals 1 Whence comes the heat produced by exercise 1 Why 
is heat in different animals proportioned to their degree of activity 1 
Contrast the warm and cold-blooded animals in this respect. 

107. What is the ordinary temperature of the human body 1 What 
is essential to comfort as to temperature in man 1 Detail experiments 
which show how high a degree of temperature can be borne. 

108. How are the evil effects of excessive heat in such cases chiefly 
prevented 1 How much does the state of torpidity vary In. different 
animals 1 On what does the degree to which a deprivation of air can ba 
borne depend 1 

109. How are some strange recoveries from drowning to be explained 1 
How far are the chemical changes described in this chapter dtpenden* 
on nervous action 1 


36 



APPENDIX. 


■m 


CHAPTER VIII. 

109. By what is the building and repairing of, the body done 
Have the vessels by which this is done, the power of selecting their ma? 
tcrial from the blood 1 

110. Illustrate the variety of structures formed from the blood by 
taking the eye as an example. Give examples of the co-operation of 
the formative vessels in their work. 

111. How is the concert of action in these vessels illustrated in the 
definite but various shapes of the structures which they make I How 
is the wonderfulness of this co-operation shown by comparison with 
the formation of a crystal 1 

112. Illustrate the agreement necessary between different neighbor¬ 
ing sets of formative vessels in the process of growth. Illustrate the 
wonderfulness of the concert of action in the formative vessels, when 
there is a change of action. How is this exemplified in certain ani¬ 
mals, as the frog and the silkworm 1 

114. How is this change of action exemplified in the enlargement of 
communicating arteries, after tying an artery in case of an aneurism 1 

115. Describe the agreement of action seen in the successive changes 
that take place in the formation, discharge, and healing of an abscess. 

116. Notice the agreement of action between the formative vessels 
and the absorbents in the cases mentioned. Are the secretions of 
organs made from the same material that the organs themselves are I 
What exception is there 1 

117. How many kinds of waste particles are there 1 By what ab¬ 
sorbents are those particles taken up that can be used again ? What 
organs probably fit them to be used again as a part of the building ma¬ 
terial ] Where is the lymph, which they compose, mingled with the 
blood 7 

118. By what are the particles that are wholly useless absorbed 7 By 
what organs are they excreted or thrown off from the body 7 Do these 
various organs excrete different parts of this waste 7 Do we know why 
this waste matter is introduced into the blood, instead of being thrown 
off in some more direct manner 1 Give some examples in which other 
functions besides excretion are performed by the same organ. 

119. What are the various functions of the skin 1 Describe its struc¬ 
ture to show how well it is fitted for these functions. 

120. How extensive is the tubing of the sweat-glands 1 In what two 
respects is the excretion from them important 7 What is the difference 
between insensible and sensible perspiration 1 What are the sebaceous 
glands 7 What purpose do they serve 1 Where are they most abun¬ 
dant 1 

121. Upon what does the rapidity of the change constantly going on 
in the body chiefly depend 1 Which has the most influence on this 
change, mental or bodily labor 1 Illustrate the influence of activity on 
this change by a comparison between the frog and the canary bird. 

122. Illustrate the same influence by a comparison between different 
parts of the body. Why does the change of the particles vary much in 
rapidity at different times 1 What is said of the mingling of life and 
death in the changes of the particles 7 



APPENDIX. 


423 


CHAPTER IX. 

123. What has been the common idea about what are called forma 
tive vessels ! By what are all the minute operations of the system per¬ 
formed ! How do the cells differ from the cells in the cellular tissue 1 

124. What do these cells contain ! What is to be said of their form 
Describe them as seen in the blood. Of what are the solid parts of the 
body composed ! 

125. How do the cells appear as seen in the Hydra 1 Upon what 
does the character of many of the textures of the body depend ! What 
is the chief difference between the various glands of the body 1 Upon 
what do the colors of various parts depend 1 How are the colors of 
flowers varied in kind and in degree ! 

126. Illustrate the selecting power of the cells. Can we account for 
this power 1 What is said of the idea that the selection is the result 
of affinity 1 What is said of the changes that take place in the con¬ 
tents of the cells ! In what two ways do cells produce other cells ! 

127. How many kinds of cells are there in the blood 1 What gives 
the red color to the blood ! What are two of the offices of the colored 
cells I How does their amount vary in different animals, and in differ¬ 
ent individuals of the human race 1 

128. Describe by the figure the manner in which absorption is per¬ 
formed on the surface of the mucous membrane in the bowels. 

129. Describe in like manner secretion by Fig. 63. 

130. Of what is the cuticle or scarfskin composed ! How many 
Hbrilla, are there in a muscular fibre! What is each one of these 
fibrillse! What takes place in them when the muscle contracts 1 
What is the cause then of the swelling out of a muscle when it acts 1 
How minute are the cells in muscles! 

131. What solid animal deposits are made by cells'! Describe the 
arrangement in the enamel of the teeth. Of what are the nerves com¬ 
posed ! 

132. What has been found in regard to combinations between the 
tubuli of the nerves 1 How are these tubuli made from cells ! In 
what other parts of the nervous system besides the nerves, are they 
found ! What is the office of the tubuli ! What is the office of the 
gray substance of the brain ! Of what is this substance chiefly com¬ 
posed ! What is said of the form of its cells 1 Where does the micro¬ 
scope show us is the beginning of life ! 

133. What is the Extent of the agency of the cells! In the forma¬ 
tion of every animal what precedes the appearance of any diversity of 
parts ! 

134. Describe the arrangement of the contents of an egg. 

135. Describe the succession of processes that take place in the yolk 
preparatory to the formation of the bird. From what material are all 
the parts of the bird made! 

136. What is the allantois, and what is its office! How can you 
prevent it from performing its office, and thus arrest the development of 
the animal! When the bird is fully formed, how is he enabled to burst 
the shell! What is the grand distinction between organized and unor¬ 
ganized substances! 



424 


APPENDIX. 


137. What comparison is made between gravitation and cell-life? 
Compare the exhibition of the Creator’s power in the minute and in the 
large operations of nature. What comparison can you make between 
the beauty of nature as seen by the naked eye, and its inner beauty 
revealed by the microscope ? 


CHAPTER X. 

139. How far are the functions of nutrition alike in animals and 
plants 1 How has the microscope shown formation to be essentially the 
same in both 1 Through what system are the uses for which the body 
is constructed secured 1 

140. Why are the functions that are performed through the nervous 
system, called functions of animal life ? Why are they also called func¬ 
tions of relation ? Through what intermediate instruments does this 
system perform its functions ? How does this system vary in compli 
cation in different animals ? 

141. How much is learned through the nerves and their subordinate 
organs, the organs of the senses ? Mention the subjects to be treated 
of in this third part of the book. What are the three parts into which 
the nervous system may be divided ? 

142. What three things are necessary to sensation ? Illustrate the 
necessity of each. What three things are necessary to voluntary mo¬ 
tion ? Describe the arrangement of the parts of the nervous system as 
represented in Fig. 72. 

144. Describe the arrangement and structure of the brain as repre¬ 
sented in Fig. 73. 

145. What part of the nervous system is most immediately essential 
to the continuance of life ? And why ? Illustrate by facts. What are 
the convolutions of the brain ? Describe the membranes of the brain— 
the pia mater —the dura mater —the arachnoid. 

146. What is the consistence of the brain? What is the arrange¬ 
ment of the gray and the white substance ? 

147. Does the arrangement of the convolutions favor the idea of the 
phrenologist? Of what is the white substance of the brain composed? 
What function is performed by it ? What tubuli transmit impressions 
from the brain? What transmit to it? What is said of the size of the 
tubuli ? 

148. What is the function of the gray substance ? In proportion to 
what does its amount vary in different animals ? Is there gray matter 
at the extremities of the nerves ? 

149. With what are the cells in the gray substance mingled ? What 
is said of the necessity of a supply of arterial blood to this substance ? 
How does the arrangement of the gray and the white substance differ 
in the brain, in the spinal marrow, and in the ganglions ? What are 
ganglions ? What are plexuses ? 

150. Why is the gray matter so largely supplied with blood ? What 
has the microscope shown in regard to the changes going on in this sub¬ 
stance ? What is said of the manner in which the nerves terminate in 
the organs of the body ? 

151. Where are the Pacinian corpuscles mostly found? Describe 
their structure. What do we know of their use ? 




APPENDIX. 


425 


152. What is there that is wonderful in the healing of a divided 
nerve 1 What do the observations of M. S&quard show? What fact 
was proved by the experiments of Dr. Haighton ? What does this fact 
show ? 

153. What nervous changes occur when a union takes place between 
parts that do not belong together ? Do the same nerves answer for sen¬ 
sation and for motion ? In what part of the body are nerves of differ¬ 
ent kinds kept separate ? How is it in all other parts ? What is the 
arrangement of the nerves that branch out from the spinal marrow ? 
W T hat two purposes do the two roots of each nerve serve ? How is this 
ascertained! 

154. Are there different nerves for different kinds of sensation 1 
How is it in the e} r e? How in the nose ? What is a nerve of common 
sensation ? What is a nerve of special sensation ? Is each nerve fitted 
for its own peculiar office ? Illustrate by reference to the nerves of the 
eye. Notice particularly the effects produced, if the nerve of common 
sensation in the eye be paralyzed. 

155. Why are different parts of the body endowed with different de¬ 
grees of sensibility ? Wliat organ is more sensitive than any other ? 
How much sensibility have the muscles ? How much have the bones ? 
W T hat fact is related to show the use of the sensibility of the skin in 
preventing injury ? What change takes place in the sensibility of inter¬ 
nal parts when they become inflamed? What benevolent purpose is 
there in this? Does a nerve, as a matter of course, have sensibility? 

156. What is true of the brain in relation to sensibility? What of 
the heart ? Relate the case given in illustration. Is the heart well en¬ 
dowed with nerves ? With what nerves is it endowed ? What is said 
of the nerves of motion in the face ? What are the appearances when 
the nerve of expression in the face is paralyzed! Why is this nerve 
called the respiratory nerve of the face ? 

157. How are the motions of expression in the face connected with 
the motions of respiration ? Describe the results when this connection 
is broken by a paralysis of the respiratory nerve of the face. 

158. How many different nerves are devoted to the eye? What are 
their different offices ? Of nerves going to the same part may one be 
palsied while another is not ? Give some illustrations. Give the case 
related by Sir C. Bell. 

159. Are the nerves of different kinds all alike in their structure and 
composition ? Why cannot the impression producing sensation be 
transmitted by the same nerve with the impression producing motion ? 

160. What has been till recently the most common theory in regard 
to the action of the nerves ? Upon what circumstances is the opinion, 
that nerve-force is identical with electricity, based ? Mention the facts 
and experiments that disprove this. 

161. In what direction is nervous action in sensation? In what 
direction is voluntary motion ? Does voluntary motion occur sometimes 
in consequence of sensation, and sometimes not ? Illustrate this. Give 
the resemblance of the nervous system to a telegraphic apparatus. 
What is true of motion caused by mental emotions? 

162. Give some examples of muscles that are wholly involuntary, and 
of muscles that are partially so. What is the difference between an 
excitor and a motor nerve ? Illustrate by reference to the respiration— 

3d* 




APPENDIX. 


4‘2fi 


the contraction of the iris—and the action of the muscular coat of the 
stomach. 

163. Why is the action of these two classes of nerves called a reflex 
action 1 Do we know what is transmitted through the trunk of a nerve 1 
Does reflex action ordinarily occur without positive sensation ? Under 
what circumstances is sensation connected with it ? Illustrate by refer 
ence to the action of the respiratory muscles, and the muscular action 
of the stomach. In relation to what class of muscles does the spinal 
marrow act for the most part independently of the brain ? 

164. What is the relation of the spinal marrow to the brain in regard 
to the voluntary muscles 1 What is true therefore of injuries of the 
spinel State now the two separate functions of the spinal marrow. 
By what arrangement are they performed ! Illustrate the modes of 
effecting sensation—motion—and reflex action. 

165. How does the brain differ from the spinal marrow as to intervals 
of rest ? Illustrate the continuous action of the spinal marrow, as seen 
in the operations that go on in the system when the brain is asleep, or is 
torpid with disease. Besides these operations, mention some of the mo¬ 
tions that can be excited through the agency of the spinal marrow inde¬ 
pendent of the brain. Explain the agency of the spinal marrow in con¬ 
vulsions. 

166. What is said of the fact, that in convulsions there is an invol¬ 
untary action of muscles that are ordinarily under the control of the 
will! Cite some facts to show that voluntary muscles act involuntarily 
more often than is commonly supposed. 

167. Explain the involuntary action of muscles in walking and other 
like acts. How is it with one who is walking in a reverie 1 What was 
formerly supposed in relation to the importance of the brain as a central 
organ of the nervous system 1 How do we know that the brain is not 
directly essential to the maintenance of life l 

168. What are the functions most essential to life! Upon what part 
of the spinal marrow do these depend ? Illustrate the extent to 'which 
the different parts of the spinal marrow are independent of each other. 
Is there any sensation independent of the brain ! 

169. Why is the system of nerves, of which I have treated in this 
chapter, called the cerebrospinal system 1 What other system is there! 
What are its purposes! What are its arrangements'! How does it 
differ in its general arrangement from the cerebro-spinal system ? 

CHAPTER XI. 

170. What two different purposes do the bones fulfil'? What bene¬ 
volent purpose is manifest in the predominance of the animal portion of 
bone over the mineral in the child ? In what two forms is bony sub¬ 
stance deposited ? How are these arranged in the flat bones 1 How in 
the long ? 

171. How are both lightness and strength secured in a long bone— 
first, in the body of the bone, and then, in its ends 1 Why are the ends 
not made like the shaft? What is the marrow of the bone? 

172. How is a bone nourished? What is the periosteum. ? Do arte* 
ries enter the solid substance of the bone ? Describe the manner in 
which circulation is carried on in every point, as shown by the micro¬ 
scope. 




APPENDIX. 


427 


173. What fluid circulates in the minute channels in bone, shown to 
us by the microscope ! What is said of the sensibility of bone ! Give 
a general description of the skeleton, noticing the variety of shape in 
the bones, and the purposes which they answer. 

175. How many bones are there in the head! How many of these 
belong to the face ! How many to the cranium 1 Describe the latter, 
as represented in Fig. 87. 

176. Why is the box (as the cranium may be called) holding the 
brain, composed of so many bones ! Describe the structure of the prin¬ 
cipal bones of the cranium. What is the difference between the join¬ 
ings of the outer and those of the inner tables of these bones ! What 
is the reason of this difference ! 

177. How are the principles seen in the construction of domes illus¬ 
trated in the cranium 1 Of what bones is the dome of the cranium 
made up! Describe the different ways in which strength is secured 
around the base of this dome. Describe especially the arrangement be¬ 
tween the parietal and temporal bones. 

178. When violence is inflicted upon the head, what is the direct cause 
of the injurious effects felt by the brain ! On what principle do the 
guards of the brain defend against this cause of injury! Mention now 
in their order the different textures through which the vibration of a 
blow must pass before it reaches the brain, pointing out their agency in 
lessening the vibration. 

179. What arrangement is there of the lower part of the frontal bone 
as a special guard against injury at that point! How is the side of the 
head, so peculiarly exposed to violence, especially guarded! What other 
organs, beside the brain, are protected by the cranium 1 

180. Describe the arrangement of some of the bones of the face. 
Describe the cavities of the nostrils, and the sinuses connected with 
them. What is the object of the great extent of surface in these 
cavities! 

181. Describe the lower jaw. How many distinct structures are 
there in the teeth! What is their arrangement! 

182. How does a tooth differ from a bone! What is the reason for 
this difference! What is the necessity for having a second set of 
teeth! 

183. Describe the hyoid bone, its position, and its connections. Men¬ 
tion other bones which, like this, are not directly connected with the 
bones of the skeleton. Of .how many bones is the spinal column com¬ 
posed ! Acting as the great pillar of the body, what does it support! 
What is the pedestal on which it stands, and in what manner is this 
pedestal made firm! While this column is thus firm, it needs to be 
flexible—how is this accomplished! Notice its different degrees of 
flexibility in different portions of it. Why is there so little motion in 
that portion that supports the framework of the chest! 

184. Besides serving as a firm pillar and a flexible chain, w r hat other 
purpose does the spinal column fulfil 1 Describe a vertebra. By what 
are the vertebrae bound together 1 

185. Describe the canal in this column for the spinal marrow. What 
is the arrangement for the nerves that pass from it 1 How are the car¬ 
tilages arranged! What two purposes do they subserve! 

186. What is there in the shape of the spinal column that acts as a 




428 


APPENDIX. 


safeguard against shocks to the brain ! What are now the three objects 
secured in the structure of the spine ! Describe the contrivance at the 
top of it, as represented in Figs. 95, 96 & 97. Compare this with the 
mounting of a telescope. What is the difference in the-two cases ! 

188. By what arrangement is the freeness of motion in the neck of 
birds made consistent with the security of the spinal marrow ! What 
is there peculiar in the spinal column of quadrupeds 1 

189. What is tire paxy-waxy ? How are the vertebrae of fishes con¬ 
structed and arranged! How is the great flexibility of the spine in 
reptiles secured ? How in the neck of the giraffe! 

190. Describe the arrangement of the breast-bone, the collar-bone, 
and the shoulder-blades. What is the use of the collar-bone, and what 
are its variations in different animals 1 How does the shoulder-blade 
differ from all other bones in the body ! 

192. Why is the socket of the shoulder-joint so shallow 1 Describe 
the arrangement of the radius and ulna, and the manner in which such 
free and varied motion is given to the arm. Describe the three parts of 
the hand. 

193. Describe the ligaments that bind the bones of the hand together. 
What is the principal object aimed at in the construction of the lower 
extremity 1 What in the upper 1 

194. Describe the thigh-bone. What is the patella! WTiat pur¬ 
poses does it answer! What part of the foot is formed by the tarsus 1 
What part by the metatarsus ? 

195. How many bones are there in the toes! How many in the 
whole foot! What object is secured by having so many bones in the 
foot! Why is the foot arched! Describe its movement in walking. 
With what are the ends of the bones tipped, and why! What is the 
arrangement of the membrane that lines the ends of the bones! 

196. What contrivance is there in the knee-joint, and in the articula¬ 
tion of the lower jaw! 


CHAPTER XII. 

’ ^6. Give the summary in $ 294, in regard to the action of the mus¬ 
cles, and their nervous connections. • 

197. What are the tendons! What is said of the relation they bear 
to the muscles—their shape—their mode of union with muscles and 
with bones—their strength—and their size! How are the muscles and 
tendons arranged in reference to convenience and beauty 1 Illustrate 
Dy the arm and the hand. 

198. Illustrate the application of the first kind of lever in the action 
of muscles—so also of the second kind. 

199. And of the third kind. Which kind is most frequently used in 
the body! 

200. What two different objects are aimed at in the application of 
these two levers! Illustrate by examples of the second kind of lever. 

201. Illustrate the same by examples of the third kind. What is the 
difference between the motion of the forearm on the arm, and the mo¬ 
tion of the lower jaw, in the application of the principles alluded to. 

203. Show how quickness is secured at the sacrifice of power in the 
case of the biceps muscle, as illustrated in Fig. 114. Under what me- 



APPENDIX. 


429 


chanical disadvantage do most of the muscles act, as represented in 
Fig. 1151 

204. Show by this figure how quickness of movement is gained in 
this case. Why is the muscle, the deltoid, whose action is represented 
in this diagram, so large 1 

205. How is the mechanical disadvantage, which thus results from 
the oblique action of the muscles, in part obviated 1 Illustrate by Figs. 
116 & 117. Describe the agency of the patella in this respect. To 
what extent is the pulley used in the arrangement of muscles 1 

206. Show the application of the pulley, as seen in the ankle. 

207. Describe the pulley arrangement of the digastric muscle. What 
is the necessity for such an arrangement 1 What other office does this 
muscle perform, besides drawing down the lower jaw, and how does it 
do it 1 

208. Describe the muscles that move the ball of the eye. 

209. What is said of the actions of opponent muscles 1 What is 
Paley’s comparison 1 Is it strictly correct ? Give some examples of the 
tonic contraction of muscles What is the cause of wry neck, and of 
squinting 1 Illustrate the compound action of muscles by Fig. 113. 

210. How does variation in the degree of the contraction of muscles 
affect the variety of motion 1 What organ peculiarly exemplifies vari¬ 
ety in muscular action 1 Give a general description of the muscles of 
the body, as exhibited in Figs. 122 & 123. 

214. What is said of the variety of size in muscles 1 What other 
parts besides the bones are moved by muscles ? How are the muscles 
arranged in reference to convenience and symmetry ? 

215. Describe a peculiar arrangement of tendons and muscles in the 
sole of the foot. Describe the arrangement of tendons represented in 
Fig. 124. 

216. Describe the complicated action of the muscles in swallowing— 
and in speaking and singing. How are the epiglottis and the larynx 
used in these acts'? W T hat is said of the ease and quickness of the 
change from the one act to the other? 

217. Show how the variety and complication of muscular action are 
illustrated in some of the general movements of the body —as walking, 
pulling with the feet braced, and balancing. Describe the operation of 
the toggle-joint. 

218. Give examples of the application of this operation in the action 
of muscles. 

219. How many muscles are there in the hand and arm? What is 
6did of the extent of the variety of their action ? Contrast the hand, 
as doing light and heavy work. Give a summary of the endowments 
of the hand. 

220. Give a description of various muscular movements that may be 
going Dn in the body at the same time. What is the muscular sense ? 

221 Illustrate the operation of it in various ways. Is this sense a 
source of enjoyment? 


CHAPTER XIII. 

222. By what alone are thought and feeling expressed? What sub¬ 
ordinate modes of expression are there ? Illustrate the fact that these 



430 


APPENDIX. 


require to be interpreted by muscular action. By what mode of muscu¬ 
lar action are thought and feeling mostly communicated 1 What rela¬ 
tion has writing to this mode of communication ! What other parts 
beside the face are brought into action in the language of the muscles ! 

223. Illustrate the extent of this language. How can we get the best 
idea of its extent 1 How do other animals differ from man in regard to 
the parts used in the language of the muscles ! W T hat passion is almost 
the only one that can be expressed by them in the countenance 1 What 
distinction is sometimes made on this ground between man and other 
animals 1 

224. What are the principal muscles that give the face expression 1 
How is a smile produced! How is sadness expressed! How do smil¬ 
ing and laughing differ in the action of the muscles 1 

225. How does weeping differ from mere sadness in muscular action! 
What peculiarity is there in muscular action in weeping from pain! 

226. To what is to be attributed the apparent expression of the eye! 
How can it be proved that the eye has no active agency in expression! 

227. What is the common notion in regard to the eye as a means of 
expression! How far is expression a result of combined muscular 
action! 

228. Describe the muscles of the face, with the action of each, as ex¬ 
hibited in Fig. 130. 

229. Describe the muscles about the mouth, as shown in Fig. 131. 

230. In what way is the expression of the face made the same in its 
two halves! What nerve governs all the muscles of expression in the 
face! What results when one of this pair of nerves is paralyzed! 

231. Is there commonly any one muscle devoted to the expression of 
any one emotion or passion 1 Does the same muscle often take a part 
in the expression of various emotions ! Explain the agency of various 
muscles—the frontal—the corrugator supercilii—the superbus. Illus¬ 
trate the combination of muscular action in expression, as shown in Fig. 
132, and also in Fig. 127—giving the differences in them. What is the 
action of the muscles in quiet sorrow! 

233. What is their state in the expression of a calm pleasure! 
What in the expression of admiration! How does temperament affect 
the state of the muscles in the two last-mentioned expressions! De¬ 
scribe the action of the muscles in the expression of rage. By what 
combination of the action of muscles are the canine teeth exposed! 

234. Describe the action of the muscles in fear. Show how it differs 
from their action in rage. 

235. Illustrate the agency of the muscles of the eyeball in expression. 
What is said of the action of the oblique muscles! 

236. Why is the intoxicated man apt to squint and to see double! 
Why does he raise his eyebrows in the effort to keep his eyes open! 
What muscles of expression are found in the faces of animals! In re¬ 
gard to what muscles is the horse specially endowed! What is said of 
the muscles that distend the nostrils in the case of man! 

237. What muscles of expression are wholly peculiar to man! Re¬ 
mark on each. What are almost the only passions that can be expressed 
by the faces of animals! What special provisions are there in some for 
the expression of rage—about the mouth, and the eye! What peculiar 



APPENDIX 


431 


phenomenon in the reflection of light is seen in the eye of the cat tribe, 
and what is the explanation of it 1 

238. Give the substance of $ 348 in regard to the combination of 
muscular action in the expression of the countenance. What is said in 

349 of the action of the rest of the body in expression ! 

239. What muscles of the body sympathize most with those of the 
face in expression ! Give examples m illustration. What effects are 
produced by mental emotions on the circulation 1 What is the expla¬ 
nation of blushing 1 What is said of the adaptation of the countenance 
to the mind as an instrument of expression 1 Draw the analogy be¬ 
tween the hand and the face in this respect. 

240. What is said of the importance of training the muscles of the 
face ! How far does beauty of countenance depend upon muscular ac¬ 
tion ! What difference is there in this respect between the living coun¬ 
tenance, and the face of a statue ! Give the remark of Addison. 

241. What is said of skill in the use of the muscles of the face as 
compared with those of the hand 1 In what cases may you see this 
skill! What is said of mistakes in interpreting the language of the 
muscles! W r hat is said of the influence of moral and mental cultiva¬ 
tion upon the countenance! 

242. Explain the expression of the countenance, as seen after death. 

CHAPTER XIV. 

243. What principles apply to the construction of the apparatus of 
the voice! Illustrate its superiority to other instruments as a musical 
instrument. What most particularly distinguishes it from them! 

244. What is said of its power of fascination ! What comparison is 
made in this respect between the voice of conversation and that of song! 
What is said of the variety of voices in the brute creation 1 

245. Into what two kinds are wind-instruments divided! Explain 
the manner in which the variation of note is produced in those of the 
first kind, by reference to the flute and the trombone. 

246. Illustrate the same point in the operation of the flute-stop of the 
organ. What influence does the width of the vibrating column of air 
have upon the note! How is the note varied in those wind-instru¬ 
ments in which the length of the column of air cannot be altered 1 
How are the variations of note produced in whistling 1 

247. What are some of the wind-instruments of the second class! 
How is the sound produced in these ! How is the note varied! Illus¬ 
trate by reference to the reed-stops of the organ. How are the various 
notes produced in the clarionet 1 Trace the analogy, in the application 
of the principles of musical sounds, between the vibrating column of 
air, the reed, and the strings in such instruments as the piano and vio¬ 
lin. Explain the relation of the tube of the reed-instrument to the reed, 
as stated in § 366. 

248. What is the trachea, and of what is it composed 1 Why are its 
rings of cartilage not perfect rings! What is the larynx ! 

249. Describe the parts of the larynx as represented in Fig. 136. 
Describe particularly the arrangement of the arytenoid cartilages and 
the vocal ligaments, as represented in Figs. 137 & 138. 

250 Describe, by means of Fig. 137, the manner in which the differ- 





432 


APPENDIX. 


ent notes of the voice are produced. Describe the apparatus of the 
voice, as represented in Fig. 139. 

252. What is the arrangement of the two pairs of ligaments ! 

253. How do we know that the lower ligaments are the true vocal 
cnords 1 Apply now the principles regulating the variation of note in 
common musical instruments to the vocal apparatus. 

254. Give Magendie’s experiment. What is said of the question as 
to what kind of musical instrument the larynx most resembles 1 Give 
the general conclusion as to the application of the great principle of 
musical sounds. What is the tube of the vocal apparatus, which an¬ 
swers to the tube of a reed-instrument ! How many outlets has it 1 
From which does the voice generally issue 1 How is it in humming ! 

255. What influence do the cavities of the nose have on the voice ! 
In what way is the reverberation in them regulated! In what two 
ways is the size of the vibrating column of air in the tube of the vocal 
instrument varied ! What influence does this tube have on the charac¬ 
ter of the voice ! How would the voice sound if it should come directly 
from the larynx, instead of passing through the tube attached to it 1 

256. What is the cause of alterations in the voice, as hoarseness 1 
Where is the difficulty when the voice is lost! In what two ways does 
the epiglottis affect the voice ! 

257. What is said of the variety and precision of the action of the 
muscles in the modulation and articulation of the voice 1 How much 
do the ligaments vary in length in producing all the variety of notes of 
which the voice is capable! Give the calculation in regard to the mi¬ 
nuteness of the muscular action in passing from one note to^another. 
How does the vocal instrument differ from others in the mode of pass¬ 
ing from one note to another 1 With what instrument can the voice be 
imitated in this respect! How does the voice of speech differ from that 
of song! 

258. What is said of the training of the muscles of the vocal appara¬ 
tus ! What is the analogy between the training of the muscles moving 
the vocal ligaments, and the training of the lips in playing on a reed- 
instrument ! What is said of skill in managing the muscles of the 
chest in speaking and singing! Give the illustration of the bag-pipe 

259. What is one of the chief causes of “throat disease” in public 
speakers ! What circumstances tend to produce this disease 1 Where 
is the voice formed in birds 1 How is the vocal tube in their case altered 
in its length for the different notes ! 

260. Describe the various parts of the vocal tube, that have an agency 
in articulation. In the articulation of how many letters is the tongue 
the chief agent! State some facts to show that the tongue is not so 
essential to the power of speech as is commonly supposed. 

261. What letters are chiefly formed by the teeth! What is lisp¬ 
ing ! What letters are chiefly formed by the lips! 

262. Why do children use labials so early and so freely! Of what 
are their terms of endearment composed in most languages! Give 
other facts stated in this paragraph in relation to the use of labials. 
Illustrate the agency of the nasal cavities in articulation. What consti¬ 
tutes a distinguishing peculiarity of many consonants! 

263. Explain the difficulty called speaking through the nose. What 
is said of articulation in whispering! 



APPENDIX. 


433 


264. How is the variation of note in whispering caused ! How can 
you observe the mechanism of the parts necessary in producing any of 
the alphabetic elements ! What is said of the common definition of 
consonants 1 Mention some of the attempts that have been made to 
imitate the articulation of the voice by mechanism. 

265. How many alphabetic elements are there, as reckoned by 
Rush! By what is the adjustment of the articulating apparatus for 
each one of them effected 1 What is said of the training of the mus¬ 
cles of the voice ! Describe the process of learning to talk in the child. 

266. What is the chief instructor of the voice ! What other organ 
assists in this instruction 1 Illustrate the fact that it is difficult for any 
but the young to acquire accurately the pronunciation of a language. 
What is said of skill in the use of the vocal apparatus 1 Compare this 
with skill in the use of other muscles. 

267. What is stammering 1 What facts are stated in regard to it ! 
In deaf mutes what is the cause of the dumbness in almost every easel 
What cases may be cited in proof 1 Give the case related by Magendie. 

268. What other cases may be cited that are more common ! Can 
deaf mutes be taught to talk! What objections are there to doing it! 

269. Explain the difference between the voice of speech and that of 
song. Illustrate the uses of the vanishing movement in speech. 

270. W r hat effect does the use of the vanish on the interval of a semi¬ 
tone produce 1 Illustrate this. What two reasons are given for the fact 
that, while every one learns to talk, there are many that do not learn to 
sing 1 

271. How is musical talent compared with other talents 1 What is 
the explanation of ventriloquism 1 

CHAPTER XV. 

271. How is sound produced! When is sound musical, and when 
discordant! 

272. What is said of the transmission of sound! What of its re¬ 
flection! Illustrate the influence of the reflection of sound in accumu¬ 
lating it. 

273. How can you prove that sound, unlike light, cannot be trans¬ 
mitted through a vacuum ! What is true of the facility of the transmis¬ 
sion of sound through solids and fluids as compared with air! Illus¬ 
trate it by facts. How is the fact, that sonorous vibration does not rea¬ 
dily pass from one medium to another, illustrated ! Upon what does the 
degree to which the vibration is lessened in passing from one substance 
to another, depend! 

274. In what cases is the. intervention of a membrane of essential 
service, and why! Give a general description of the process of hear¬ 
ing. Describe the apparatus of hearing, as represented in Fig. 148. 

275. What is the object of the external ear! What is the use of 
its ridges and prominences ! 

276. What is said of the external ears of animals in comparison with 
nan 1 Describe the tube of the ear. By what two means is it guarded 
against intruders! Describe the drum of the ear and the little bones. 

277. What is the arrangement of these bones! What are their con¬ 
nections, and how do their muscles act upon them! Flow does the cav- 

37 



434 


APPENDIX. 


ity of the tympanum communicate with the mouth, and why ! What 
part of the ear is the essential part of the apparatus 1 How much of 
the apparatus may be destroyed without entire loss of hearing ! Give 
the case related by Sir Astley Cooper. 

278.. Describe the parts of the labyrinth. In what different ways 
may deafness be produced by defects in this part of the apparatus ! 

279. Why is it better that the vibrating substance in the labyrinth be 
a fluid than a solid or a gaseous substance! What is the use of the 
chain of bones 1 Describe the chalky concretions, and their use. 

280. What is the use of the fenestra rotunda? Describe the arrange¬ 
ment of the cochlea. 

281. In what two directions is the vibration of the fluid in the laby¬ 
rinth transmitted! What is the course of the vibration in the cochlea! 
What is the arrangement of the membranes in the cavities of the laby¬ 
rinth ! W hat is the arrangement of the nerves in the semicircular canals! 

283. Describe the distribution of the nerve in the cochlea. In what 
two ways does the nerve here receive impressions from the vibration of 
the fluid! 

284. Describe now, step by step, the process of hearing. Is all our 
hearing done in this way! Give examples of hearing through the bone 
enclosing the labyrinth. How does the apparatus of hearing in fishes 
differ from that of man! W T hy is it less complicated than in animals 
that live in air! 

285. Mention some particulars in which the ear of birds differs from 
that of man. What is the simplest form of the hearing apparatus 
found in animals! What are some of the •suppositions in regard to the 
ollices of particular parts of the labyrinth! What is true of them! 
What part of the process of hearing can we trace and understand' 1 
How much do we know about the transmission of the impression from 
the fluid through the nerve to the mind 1 

286. Is it true that the eye is a more wonderful organ than the ear* 
What is said of the mingling of the spiritual and the simply mechani 
cal in the process of hearing ! What are to be considered the two ends 
of the apparatus of hearing! 

CHAPTER XVI. 

287. Into what two parts may the process of seeing be divided! 
What principles govern the construction of the mechanical part of the 
apparatus! What is the object of its arrangements! How is the sec¬ 
ond part of the process executed! How does the transmission of light 
resemble that of sound 1 What is the refraction of light! Illustrate 
by Fig. 156. 

288. How are the rays bent in relation to a perpendicular when they 
pass from a denser into a rarer medium! How, when they pass from 
a rarer into a denser! How are the rays refracted when they pass 
through a medium that presents a convex surface! 

289. How are the rays refracted -when they pass through a medium 
which has a concave surface! 

290. How many coats has the eye! Describe the arrangement of 
the parts of the eye, as represented in Fig. 159. What is the use of 
the sclerotic coat! How is the cornea fitted into it! What is the color 



APPENDIX. 


435 


of the choroid coat, and to what is it owing 1 Of what is the retina 
chiefly composed ? What are the three humors of the eye? Describe 
the chamber in which the aqueous humor is. What is the consistence 
of the crystalline numor or lens ? Describe the vitreous humor. Why 
is it called vitreous? 

291. Describe the various parts as they are more minutely delineated 
in Fig. 160. How is the aqueous humor formed? How is it continu¬ 
ally changed ? Describe the membrane called the conjunctiva. What 
are the ciliary processes ? Describe their arrangement. 

292. What is their use ? How are images of objects formed upon the 
retina! How can the fact, that such images are formed, be proved ? 

293. Why are these images inverted ? What is the plan of a camera 
obscura ? Compare the eye in its arrangements to an instrument of 
this kind. 

294. What qualities are needed in the cornea? How is its transpa 
rency secured ? Why is it more convex than the sclerotic coat ? On 
what does the color of the iris depend? What is the principal office of 
the iris ? By what arrangement of its muscular fibres are its motions 
effected? How does the pupil differ in carnivorous and herbivorous 
animals ? 

295. What is the office of the crystalline lens ? What is its shape 1 
Its structure ? What disease has its seat here ? What are the three 
modes of remedying the difficulty ? What two purposes does the cho¬ 
roid coat serve ? Why is its color dark ? 

296. What is the state of the choroid coat in the albino? What 
gives the bright red or pinky hue to the iris in his case ? How does the 
color of the choroid coat vary in different animals ? What is the cha¬ 
racter of the retina, and its office ? Trace the analogy between the 
optic nerve and the other nerves of sense ? What resemblance is there 
to the nerve of touch in its termination ? What is the defect in the opera¬ 
tion of optical instruments, called spherical aberration, and how is it 
obviated in the eye ? 

297. What is the difficulty in the operation of a common lens, called 
chromatic aberration ? How is this obviated in the lens ? How in the 
eye ? 

298. Contrast the eye with the telescope in regard to the facility with 
which the eye accommodates itself to objects at different distances. In 
what two ways is this accommodation effected ? 

299. By what defects in the structure of the eye in the near-sighted 
is this power of adjustment counteracted ? How is this difficulty obvi¬ 
ated ? In what way is near-sightedness often produced ? What is the 
difficulty in the far-sighted? How is it obviated? At what different 
periods of life are these two defects apt to appear, and why ? How is 
the fact, that objects appear in their right position, although their images 
are inverted on the retina, sometimes accounted for ? 

300. What objection is there to this explanation ? Upon what erro¬ 
neous idea are such explanations based ? Do we really know how the 
mind gets the right idea of the relative position of objects ? 

301. What is necessary to single vision in regard to the two images 
formed in the two eyes! Why do you see double when you press one 
of the eyes a little out of its place ? What is necessary to single vision 
in the action of the muscles ? Why does the intoxicated man often see 



<136 


APPENDIX. 


confusedly, or even sometimes double ? Relate and explain the case 
given to show how disease may produce double vision. Why is there 
not double vision ordinarily in squinting 1 

302. When are the two images in the eyes alike ? In what cases are 
they unlike ? Relate the experiment given in explanation. How is it 
that in such a case, while there are two images, and therefore two im¬ 
pressions sent along the two optic nerves, yet the impression on the 
mind is single ? How does a person who has but one eye, acquire the 
idea of solidity 1 

303. Explain Professor Wheatstone’s stereoscope on the principles 
developed in § 454. 

304. Mention the particulars in which the harmony of action in the 
two eyes is wonderful. 

305. Notice the correspondence between the two eyes in that part of 
the process which belongs to the optic nerves. What peculiarity is there 
in the arrangement of these nerves 1 Do we instinctively perceive the 
size, distance and figure of objects, or is it an acquired power ? Relate 
in illustration the case given by Cheselden. 

306. How does the experience thus related compare with the experi¬ 
ence of the child in learning to see 1 Give the analogy between learn¬ 
ing to see and learning to walk or talk. In learning to appreciate the 
sizes, shapes and distances of objects, what sense acts as the educator 
of vision 1 What is said of the frequency of mistakes in vision ? W T hat 
of skill in seeing ? What is the visual angle ? 

307. Can we get a correct idea of magnitude by the visual angle 
alone 1 Illustrate by the Figure. What circumstance must be known 
in regard to an object, in order to have our estimate by the visual angle 
correct 1 Mention another means that we use in connection with the 
visual angle. Give examples of mistakes that we are apt to make in 
the use of this means. 

308. Illustrate the manner in which we get ideas of the magnitude of 
objects by comparison. Show how we sometimes are made aware of 
our dependence on this source of evidence. Why does the moon ap¬ 
pear so large when rising ? Explain the use of the muscular sense in 
acquiring an idea of the size and distance of objects. What use is 
made of it in looking at very near objects'! W’hat is said of our consci¬ 
ousness of the effort in doing this 1 

309. Why can you not judge accurately of the locality of very near 
and minute objects when you use but one eye'! What do we observe 
in regard to the use of the convergence of the eyes, when we look at 
the eyes of others? How far is seeing a mental process? What is 
said of the common notion, that it is a simple and easy process ? What 
is said of the training required for its performance ? 

310. Do all the images formed on the retina transmit impressions to 
the mind? Illustrate by reference to squinting. Also illustrate in 
reference to ordinary vision by an experiment. Explain this by 

311 Show now how it is that, notwithstanding the facts stated in 
§ 464, we are not conscious of seeing double. Show too how we can 
by an effort of the will have this consciousness. 

312. What is the point of distinct vision, as it is called? Show how 
the mental attention makes use of this—how in looking at an object-^ 



APPENDIX. 


437 


in reading—in looking at a prospect 1 Why do we seem to 6ee the 
whole of a page or of a prospect at once with equal distinctness 1 
How far do we see the whole of a page or a prospect at once ! What 
is said of the minuteness and correctness of the pictures formed on the 
retina 1 

313. How do we in part estimate the motion of objects! W T hat is 
said of the delicacy of the process by w hich this is done 1 Illustrate 
the frequent erroneousness of our impressions in regard to motion. 

Why is it that when we are moving rapidly, near objects seem to fly 
back, and distant objects seem to go along with us 1 Illustrate by the 
Figure. 

314. What is said of the rapidity with which impressions received 
from the images on the retina succeed each other '! Show how this 
may be measured by experiment. To what is the difference in time 
required for distinct transmission in different individuals owing 1 Trace 
the analogy between this difference and that which we see in different 
individuals in regard to the use of the muscles. 

315. Explain the Thaumatrope. How is the eye situated so as to 
protect against injury ! How does the cushion of fat on which it rests 
serve to protect it! In what two ways does the muscle that closes the 
eyelids serve as a protection to the eye! 

316. How is it protected by the eyelashes ! How by the eyebrows ! 
How are the eyelids constructed in reference to the protection of the 
eye! How do the tears serve as a protection ! Why do Ashes have no 
tear-apparatus! 

317. Describe the arrangement of the tear apparatus. Why do the 
tears overflow the edges of the eyelids when they are abundant ! What 
arrangement of glands is there on the eyelids ! What two purposes 
does the oily substance formed by them serve! How are the tears con¬ 
ducted into the mouths of the ducts when the eyelids are closed! De¬ 
scribe the nictitating membrane in the eyes of birds. 

CHAPTER XVII. 

318. Give the recapitulation presented in § 476. 

319. What is said of the brain as the organ of the mind! What 
facts show that motion and sensation are dependent on the brain! 
How does it appear that the mind thinks only by means of the brain! 
How is life continued when sensation, motion, and thought are stopped 
by compression of the brain! How does the variation of the degree of 
compression vary the effect on the mental functions! How is the de¬ 
pendence of the mind on the brain shown in disease 1 

320. Of what is insanity always the result! How do moral causes 
produce it! If the mind were separate from the body, could insanity 
be produced in it! Can the disease in the organization in insanity, 
be always discovered in an examination after death! Describe the situ¬ 
ation of the brain and its immediate connections. 

321. What is said of the face ! Illustrate the rapidity of the commu¬ 
nication between the mind and the different parts of the body. In exe¬ 
cuting muscular motion skilfully, is any assistance derived from a know¬ 
ledge of the particular muscles 1 By what arrangement is the mind 
enabled to excite so accurately the motion of the muscular fibres 1 

3r 



438 


APPENDIX. 


322. Upon what besides combined action in the muscles does the end¬ 
less variety in motion depend ! Mention some cases in which we best 
realize the variety and accuracy of the messages sent from the brain tG 
the muscles. What is said of the training of the organs of sense and 
of motion 1 What of the amount of knowledge acquired by the child 
in the first years of his life 1 

323. Describe the training of the muscles in the child. What is true 
of what is called native grace 1 What is said of the training of the 
muscles of the face ! 

324. What is said of skill in the use of the muscles 1 What is said 
of the training of the senses 1 How do other animals differ from man 
at the first in the use of the muscles and the senses ! How do they dif¬ 
fer from him in the amount of skill that training gives ! 

325. Illustrate the fact, that the senses and muscles are mutual teach¬ 
ers in their training. How does the dependence of the muscles on the 
senses differ from that of the senses on the muscles ! What fact illus¬ 
trates the absolute dependence of the muscles on the senses 1 In the 
education of the muscles and the senses, what is, strictly speaking, 
educated or trained 1 Illustrate by reference to the idiot and the deaf 
mute. 

326. What is said of the muscles of the face in the idiot 1 Why 
does not the education of the muscles extend to those that are involun¬ 
tary 1 

327. What difference is there in the different stages of the training 
of the muscles in the degree of cognizance which the mind takes of 
their action 1 Illustrate by reference to learning to walk, to read and to 
sing. What has been the general belief in regard to the means of 
communication between different minds ! 

328. What is claimed by some on this point in regard to what is 
called animal magnetism ! What has always been found to be true of 
this when its pretensions are properly tested ! Illustrate the manner in 
which this was done in one case. 

329. What is said of the illustrations afforded by animal magnetism 
of the influence that can be exerted upon the body through the mind ! 
To what diseased states is the condition produced in the subject analo¬ 
gous ! Does the explanation of the phenomena show that there is any 
true magnetic influence in the case 1 

330. What is said of the mingling of moral and physical perversion 
in the subjects of animal magnetism ! What is said of suggestive 
influences ! 

331. What is said of the exaltation of the powers of the senses in 
the subjects of animal magnetism! What is true of clairvoyance, so 
called! What is said in the note of test evidence! Give the fact 
stated in illustration. 

332. What part of the brain has an especial connection with the 
mind ! What is the chief office of the cerebellum! Give the evidence 
from comparative anatomy on which this point is settled. What expe¬ 
riments lead to the same conclusion ! What two reasons are given why 
the evidence on this point from disease is defective! What fact has 
Deen observed in cases of disease of the cerebellum! What negative 
testimony is sometimes afforded by disease in regard to the office of the 
cerebellum! 



APPENDIX. 


439 


353. Give the summary of results arrived at by studying the compar¬ 
ative physiology of the nervous system, as stated in $ 502. What is 
said of the comparative amounts of the white and the gray substance in 
the brain ! \N hat are the two sources of evidence in regard to the func¬ 
tion of the gray substance ? 

334. AN hat evidence is there in regard to phrenology from the arrange¬ 
ment of the gray substance ? What is the conclusion from all the facts 
collected in relation to the external examination of the head ? What 
evidence is the real test of the pretensions of phrenology ? 

335. What is true of the pretended locality of organs in the region 
of the frontal sinus 1 What of the organs said to be in that part of the 
head where the cerebellum is 1 What is the only fact that seems to give 
countenance to phrenology ? Why does this fact fail to prove that the 
special seat of the intellectual faculties is in the upper and front part of 
the head ! What evidence have we on this point from the phenomena 
furnished by disease and injuries 1 

33G. What is the facial angle 1 What is the difference in regard to 
this between the skull of the European and that of the African ? 
What between the skull of animals and that of man ! What is the 
common measure of this angle in ancient statues of deities and heroes'? 
What is said of the rule, that the amount of intelligence, both in man 
and in animals, is proportioned to the amount of the cerebrum? 

337. What facts show that size is far from being the only measure of 
power in case of the brain? In studying the comparative physiology of 
the brain, what significant fact do we find when we come to pass from 
the higher animals to man? Of what character is the mental difference 
between them and man ? What is said of the definiteness of the dis¬ 
tinction between man and animals ? 

338. What note ought to be made of this distinction by the compara¬ 
tive physiologist ? What is said of the intimacy of the union between 
the mind and the body ? What might we infer from the closeness of 
this union in regard to death, if we had no Revelation ? 

339. What is said of the supposed independence of the mind on the 
body ? Is there proof that mind is of itself indestructible ? What are 
the three sources of our knowledge in relation to the connection of the 
mind and the body ? What is the consequence if we rely upon any one 
of these alone ? What is the alternative to which one is driven, if he 
confine himself to the evidence which physiology furnishes ? What 
course is commonly pursued by those who take this narrow view of the 
subject! 

340. What is said of the distinction between organized and unorgan¬ 
ized matter ? What are the common suppositions in regard to the en¬ 
dowment of organized or living matter? What is said of those endow¬ 
ments of living matter that are connected with the nervous system? 
What question now arises in relation to intelligence in its connection 
with matter ! 

341. What does physiology show us in regard to this connection ? 
Point out the deficiencies of its teaching in relation to the nature of this 
connection. What is the tendency of its presumptive evidence ? Look¬ 
ing at the subject solely in the light of physiology, what would be the 
conclusion in regard to the dependence of mind on organization, when 
we observe the origin and growth of a thinking animal? What bear- 



440 


i 


APPENDIX. 


ing on this point has the fact, that the intellect grows with the brain, and 
appears at last to perish w ith it 1 

342. What is said of the evidence that may be drawn by the physi¬ 
ologist from the design obvious in the efforts of the mind ! Trace the 
analogy, in this respect, between mental phenomena and those that we 
see in the common operations of life, both animal and vegetable. Show 
how the analogy holds good in the accommodation to varying circum¬ 
stances in the cases cited. What is the extent of the analogy seen in 
the phenomena alluded to 1 To what idea has the contemplation of this 
analogy sometimes led 1 

343. Give examples of phenomena in vegetable life, that are often 
called instinctive. What fact in comparative physiology is strongly ad¬ 
verse to materialism 1 In which direction, however, on the whole, does 
the evidence from physiology, taken alone, preponderate ? 

344. State the ground of the great need which the physiologist has 
of the evidence from other sources beside his physiology. What is the 
testimony of consciousness in relation to the independence of the soul 
in its action 1 What in regard to its responsibility for its acts 1 How 
far is this testimony acted upon by all, when physiological speculations 
are left out of view ? 

345. What does the evidence from consciousness show us in relation 
to the connection of the mind with the material organization ? To what 
alternative does it'drive us'? How is this testimony of consciousness 
treated by the Bible ? Illustrate our dependence on the Bible for the 
proof of the soul's immortality. 

346. How may the discrepancies in the evidence from physiology in 
regard to the connection of the mind and the body be cleared up ? 

347. What is said of the character of the evidence drawn from con¬ 
sciousness and Revelation 1 What is said of the presumptive evidence 
from physiology in comparison with it! What is said of the present 
moral tendencies of physiological investigations 1 

CHAPTER XVIII. 

347. What was Lord Monboddo’s idea of the development of man ! 

348. What recent theory has an analogy to this 1 What is true of 
man and animals in relation to instinct and reason 1 Do we know what 
the nature of instinct is 1 Which can be understood best, the actions 
of instinct or those of reason 1 Illustrate this point. 

349. What seems to produce the actions of instinct 1 What influ¬ 
ence does the intelligence of the animal exert upon them 1 What is 
said of the invariableness of the actions of instinct 1 

350. Describe the nests of the Baya and the Tailor Bird. 

351. What is said of the perfection of the actions of instinct"? Why 
are the cells of the honevcomb made hexagonal ? Describe the arrange¬ 
ment of the ends of these cells. Give the fact stated in regard to the 
angle made by the surfaces at their ends. 

352. How is the perfection of the actions of instinct seen in animals 
that live in communities'? Describe the structure of a w r asp’s nest. 
Give the description of the habits of the beaver. 

354. In what respect may instinct be said to be blind ? Illustrate bj 



APPENDIX. 


441 


reference to animals that provide for a progeny which they are never to 
see. 

355. Why is it often difficult to distinguish between the results of 
reason and those of instinct ! What would be true of instinct if it 
were at all rational! Under what circumstances is there perfection in 
the actions of instinct ! Under what circumstances does it fail 1 Con¬ 
trast instinct and reason in this respect. Give some illustrations of the 
characteristics of instinct alluded to. 

356. Give Mr. Broderip’s account of the beaver. If the beaver in this 
case had been guided by reason, what would he have done 1 How far 
is the care that animals take of their progeny governed by a blind 
instinct 1 What is said of the temporary character of parental affection 
in their case ! In what case is there no affection at all! 

357. What degree of intelligence is shown in the power of imitation 
in animals! How do animals show that they reason ! How far did the 
beaver, whose story is given in § 541, reason 1 How does the character 
of the inferences made by animals differ from that of those made by 
man! Illustrate by reference to Newton and his dog. Of what are the 
inferences made by animals the results ! 

358. When the processes of thought in animals are extended and 
complicated, what is true of them ? Illustrate by examples the extent 
to which mental association may be carried in the animal. 

359. How do animals learn the relation of cause and effect! Illus¬ 
trate by examples. How does this knowledge of cause and effect differ 
in man and in animals ! Is the mental difference between man and 
animals one of degree only! 

360. What attribute constitutes the great superiority of the human 
mind 1 Show how this attribute is the origin of language in man. 
Wffiat is the character of the language of animals ! Why cannot they 
have a language of arbitrary signs ! What is the source of man’s be¬ 
lief in a Creator! Illustrate this point. Is this belief implanted in the 
mind 1 What two suppositions have been offered in relation to con¬ 
science 1 

361. What is said of the doubts which some entertain as to the exist¬ 
ence of conscience! What is true of those cases in which animals 
seem to some to have a moral sense! Illustrate the fact that in common 
language we recognize the difference between man and animals as to 
the possession of a conscience. Give a summary of the mental differ¬ 
ences between man and animals. 

362. Give the gradations which we find in the nervous system as wo 
trace the animal kingdom upward. Why does instinct collect no expe¬ 
rience ! What is the difference between the two kinds of reasoning, 
before spoken of, in collecting experience! What is said of the amount 
of improvement of which some animals are capable by means of the 
lower order of reasoning! 

363. What is the basis of improvement in man! What ordinarily 
constitutes the intellectual superiority of one man to another! In what 
consists the merit of an inventor or discoverer! Illustrate by reference 
to Jenner. What is the difference between the capabilities of instinct 
and those of reason in the rapidity of their development! Which form 
of reasoning is developed first! 

364. Is the higher reasoning to some extent developed quite early! 




442 


APPENDIX. 


What is said of its deficiency in those cases in which the organization 
is defective ! What is said of the achievements of this reasoning power] 
What of the separation it makes between man and animals 1 What is 
said of the slowness of development of man’s physical structure 1 . 
What is the general law as to the development of capabilities, both men¬ 
tal and physical! 

365. What is said of the prominence generally given to the difference 
between man and animals in regard to physical endowments 1 Illustrate 
by reference to the hand. In all animals, to what are bodily endow¬ 
ments suited ] Mention some bodily endowments in which some animals 
excel man, and state the reason. In what respect is man most signally 
superior to animals in physical endowment 1 Illustrate this by refer¬ 
ence to the hand and the vocal organs. 

366. Illustrate the same point by the general motions of the body. 
What is said of the human form in repose 1 How do we get the most 
perfect idea of the superiority of the human organization 1 

CHAPTER XIX. 

367. Mention some of the contrasts which we find on looking over 
the human race. How many varieties of the race are commonly reck¬ 
oned 1 What are the characteristics of the Caucasian variety 1 

368. What are the characteristics of the Ethiopian varieties—the 
Mongolian—the American—the Malay! What is said of the extent 
to which the race may be divided into varieties ! 

369. What is said of the way in which national differences are pro¬ 
duced ! What is the opinion of most naturalists in regard to the pro¬ 
duction of the races! What is the doctrine of Professor Agassis and 
others! State the grounds on which he bases his doctrine. 

370. What is his opinion in regard to climatic and other influences ! 
What is his opinion of the history given in Genesis! Are the different 
branches of the race in his view different species, or mere varieties ! 
What is the distinction between a species and a variety! 

371. Mention the influences included in the expression, climatic and 
other influences. What is said of the influence of climate! What is 
the circumstance which has most influence in producing varieties in man 
and in animals! What is included in the term domesticationl What is 
the precise question in regard to climatic and other influences! 

372. Mention some facts that show that climate has a great influence 
on the color of the race. What influence do intellectual and moral 
causes exert upon the shape of the head! 

373. What is said of certain changes in form produced by causes, the 
operation of which we do not understand! What are the three differ¬ 
ent types of form in the head stated by Dr. Pritchard, and by what 
causes are they produced 1 State in regard to each :—the prognathous 
—the pyramidal —the oval. Give some facts showing that these types 
are convertible into each other. 

374. What is said of the insensible gradations by which the varieties 
of the race pass into each other! What two objections are brought 
against the aileged competency of climatic and other influences to pro¬ 
duce the varieties of the race! What great fact is a sufficient reply ta 
these objections! State and illustrate this. 



APPENDIX. 


443 


375. Apply this fact in explanation of the production of the varieties 
of the human race. What is said of the analogy thus drawn between 
man and animals, in comparison with that which Professor Agassis has 
tried to establish ! What consideration weakens his analogy 1 

376. If the climatic and other influences appear to any one incompe 
tent to produce the varieties of the race, is he driven necessarily to ad 
mit its multiple origin 1 What is said of the occasional introduction oi 
new causes by the Creator! Upon what do our calculations upon the 
regularity of nature depend! What is said of the change in the age 
of man effected at the time of the flood 1 W'hat is said of the occa¬ 
sional appearance of new diseases 1 

377. What is said of the convulsions which have evidently taken 
place in the earth! Does it make any difference to the argument, 
whether the results came directly from causes, or from a chain of causes 1 
Apply the argument to the production of the varieties of the race. 
What is said of the objection to the argument, that it is supposing a 
miraculous interposition 1 

378. Is the supposition thus made needed 1 What is said of it in 
comparison with the supposition of Agassiz 1 On what principles is the 
testimony of the Bible as to the origin of the race to be interpreted ! 
What are the main facts which it gives in relation to it! How is the 
truth of its testimony confirmed! 

379. Of what force is analogical and presumptive evidence in oppo¬ 
sition to it! Is any fear to be entertained in regard to bringing the 
Bible to the test of ascertained facts ! If the account in Genesis be 
true, to what alternative are the advocates of the multiple origin of the 
race driven! How does it appear that the truth of the Bible and the 
unity of the race must stand or fall together! Does the argument hold 
good, even if the Mosaic account be considered a myth! 

380. What is the general conclusion in view of the whole subject! 
What moral bearing has the doctrine of the unity of the race 1 What 
is said of the pretended resemblance between the Ethiopian variety and 
the monkey tribe of animals 1 

CHAPTER XX. 

381. What is said of the diversity in the manifestations of life! 
How is life always the same in relation to its origin! Remark on the 
wonderful variety of results worked out by the vital force beginning in 
a simple cell. How is life always essentially the same in its processes 
as well as in its origin! 

382. Do we know what life is ! How does the vital force differ from 
such forces as light, heat, and electricity, in regard to its power of diffu¬ 
sion ! How in regard to self-generation 1 How in regard to the variety 
of its effects! 

383. Do we know whether life is one thing! What is said of the 
supposition, that the principle of life resides chiefly in the blood! What 
are the relations that exist in living bodies between the laws of chemis¬ 
try and mechanics and those of life! Illustrate this point. What i3 
said of the materials of which the human body is composed, and of the 
degree of heat in which they are kept! 

384. Show the difference in the operation of heat on dead and on liv 



444 


APPENDIX. 


ing matter, as seen in the egg. How is the power of the vital force ex¬ 
hibited in the uniformity of the heat of the body ? What is said of the 
changes going on by the operation of the vital force 1 Remark on the 
dormant condition of this force in the case of seeds. 

385. Remark on the analogy between the hibernation of animals and 
the state of most of the vegetable world in winter. What portions of 
the human system are some of the time dormant, and why 1 What is 
the most mysterious circumstance in regard to the vital force ? Show 
how the soul and the vital force are two distinct, and, in some measure, 
opposing forces. In what different senses are they both present every¬ 
where in the system ? 

386. What is said of the development of the soul in the body 1 
What of the mystery of this connection ? What is said of the limit of 
the vital force 1 What facts show that the endowments of life are not 
commonly all destroyed at the moment of death 1 

387. What is the distinction between systemic and molecular death 1 
What three great systems of the body are each essential to the continu¬ 
ance of life 1 How may death begin in the circulating system 1 \ Give 
the three classes of causes by which death may begin in the respiratory 
system. 

388. Give examples of death beginning in the nervous system. Illus¬ 
trate the fact, that death is commonly a complex event. What is said 
of the signs of death 1 

389. What is said of the clearness of the evidence in all ordinary 
cases in regard to the fact of death 1 In the very few cas'es in which 
there is any doubt, what course should be pursued ? What light can 
physiology give us in relation to what is beyond this life 1 What is 
said of the conjectures on this subject which its investigations may 
prompt 1 


CHAPTER XXL 

390. From what two sources are the rules of hygiene to be learn¬ 
ed 1 How far is a knowledge of physiology necessary to a proper 
understanding of these rules 1 

391. What division of topics should be made in the subject of 
hygiene 1 What points in the hygiene of digestion have been before 
noticed 1 What is said in regard to the amount of food needed by the 
body 1 How can we know what this amount is 1 

392. What errors are committed in regard to quantity of food 1 From 
what causes is too little food sometimes taken 1 What is said of the 
intervals between our meals 1 

393. What is said of eating regularly ? What of the different kinds 
of food? What of fruits 1 What influence has the mind on digestion? 

394. What is the general statement in $ 625 in regard to the hygiene 
of respiration 1 In what two ways is the free access of the air to the 
’ungs interfered with 1 What general rule is given as to dress in re¬ 
gard to the chest? In what ways does compression of the chest occa¬ 
sion disease ? 

395. Why ordinarily is the influence of defective aeration (or airing) 
of the blood not appreciated ? 

396. What influence has muscular exercise on the development of 



APPENDIX. 


445 


the organs of the body I How is it a preservative against disease ? 
What is said of violent exercise ? What is the change going on con¬ 
tinually in all parts of the body 1 What two conditions are necessary 
to the proper performance of this change ? 

39?. What is said of the discharge of waste matter from the system'? 
What organs effect this discharge ? How much matter is discharged 
from the skin ? 

398. How is the animal heat produced ? How does exercise increase 
it ? What influence has the quality of the blood upon it ? What is 
essential to a comfortable temperature of the body ? When one is too 
much heated how is the extra heat disposed of? What is the object in 
covering the body with clothing and in surrounding it with heated air ? 
What is said of cold as a cause of disease ? 

399. What are our means of guarding against cold? How should 
we regulate the amount of clothing ? What is said of guarding against 
cold when the body is in a state of rest? 

400. What is said of warming houses ? Why is the influence of 
cold in producing disease commonly so little appreciated? Under what 
circumstances does cold act as a stimulant ? 

401. What rules should be observed in the use of cold bathing? 
What are the best times for using it? What occasions the wear and 
tear of the system? 

402. When is most of the repairing of the system done ? What is 
said of the relation of exercise to health ? What effect has it on the 
muscles themselves ? What on the other textures ? How does it pre¬ 
pent deformity ? 

403. What are the two causes of the common deformity of the spine ? 
Explain their action. Why is this deformity found so much more 
often in females than in males ? How much influence has posture in 
producing it ? 

404. What especially debilitates the muscles of the back in the 
female? Illustrate the necessity of having exercise varied—also of 
having it general. What is said of gymnastics and calisthenics ? 

405. What is said of having the exercise habitual? How does too 
much exercise do harm ? What is said of having the exercise agree¬ 
able ? What is said of the hygiene of the senses ? 

406. What is said of the necessity of seasons of rest for the brain ? 
What significant fact in regard to insanity shows this ? What is said 
of the conditions under which the mind can perform much labor without 
harm? What is said of overworking the brain during its growth? 
What of the manner in which the child’s mind is ordinarily exercised ? 

407. What two mental causes acting together injure the health and 
sometimes produce insanity ? What influence has the regulation of the 
passions on the health ? On what portions of the system do alcohol 
and tobacco chiefly act ? What is said of alcoholic simulants ? 

408. Show how tobacco may act indirectly as a stimulant. What 
are its effects on the system ? To what class of persons is it especially 
injurious ? What is the evidence in regard to the influence of tea and 
coffee? 

409. W T hat is said.of emanations from filth as producing disease ? 
Give a summary of the chief causes of disease. Is disease commonly 

38 



446 


APPENDIX. 


produced by any one of these causes alone ? What is said of our con¬ 
trol over these causes ? 

410. What other causes of disease are there 1 To what extent do 
they act compared with those mentioned in § 674 1 How may we often 
escape their influence 1 What is said of the comparative value of pre¬ 
ventive and curative measures ? Illustrate the prevalent error on this 
point by reference to consumption. From what does the common 
neglect of preventive measures arise, and how can this be obviated? 



INDEX 


(The numbers refer to the pages.) 


Aberration, spherical..296 

chromatic.297 

avoided in the eye.297 

Absorption. 3 

by lacteals. 58 

by lymphatics.117 

by veins.118 

by cells.128 

Abscess, concert of action in. .115 
Aeration of the Blood, how 

done.86, 102 

how interfered with.394 

Agassiz, his doctrine of the 
multiple origin of the hu¬ 
man race.369 

Air, composition of and changes 

in it by respiration.101 

agency of plants in keeping 

it pure.104 

necessity of a good supply of 

it to health.394 

Air-cells of the lungs.86 

importance of their function. 94 
harm done in compressing 

them. 95 

Air-sacs in birds.100 

Alcoholic Stimulants, their in¬ 
fluence on health.407 

Alimentary Canal, meaning of 

the term. 15 

of different lengths in differ¬ 
ent animals.60 

Allantois.136 

Aneurism...65, 69 

Animals, distinctions between 

them and plants.21 

intelligence of.357 

their associations of ideas.. .358 
their mode of learning rela¬ 
tion of cause and effect.. .359 


Animal Magnetism. .327 

Aorta. 65 

valves of.. 76 

Arm, bones of..192 

Arteries, why so called. 72 

why made strong. 65 

situation of. 67 

how to stop their bleeding,.. 69 

Articulation of the voice.259 

Arytenoid Cartilages.249 

Assimilation. 15 

Balancing, action of muscles in. 217 
Bathing, how it should be 

practised.401 

Baya’s nest.350 

Beaver, habits of.350 

Beauty, regard to in the ar¬ 
rangement of the muscles. 197, 
207, 214 

Birds, respiration of..100 

spinal column of.188 

vocal apparatus of..259 

Blood, its changes.72 

its course. 73 

variety of textures made 

from it.110 

cells in it.125, 127 

life in.383 

Bones, composition of. 37 

uses of..170 

insensibility of..173 

very sensible when inflamed. 155 

marrow in.171 

various shapes of.173 

of the head.175 

of the nose.'.180 

of the leg.194 

of the foot.195 

Bony socket of the eye.179 






























































448 


INDEX 


Brain.144-146 I 

how guarded from violence. .178 

organ of the mind.319 

its situation and connections 320 

size of as measure of the 

intellect.336 

its developmeut influenced 

by mental activity.372 

hygiene of.406 

Breast Bone.88 

Buccinator Muscle.229 

Calisthenics.404 

Capillaries. 65 

their agency in keeping up 

the circulation. 70 

Carnivorous Animals.43, 60 

Carbonic Acid Gas, thrown olf 

from the lungs.101 

where formed.102 

quantity of it discharged 

from the lungs.103 

absorbed by plants.104 

Cartilage. 37 

Cartilages joining the ribs to 

the breast bone.88 

between the vertebrae.185 

Camera Obscura.293 

Carpus.192 

Cataract.295 

Causes, evidence that new ones 
have been introd uced since 

the original creation.376 

Cells, the true formative ves-' 

sels.123 

their shape.124 

seen both in fluids and solids. 124 

their contents.125 

their selecting power.125 

their operation incomprehen¬ 
sible.126, 137 

some make other cells.126 

two kinds in the blood.127 

cells perform absorption.128 I 

and secretion.129 

fibres of muscles made up of 

cells.130 

cells make teeth, nails, &c. .131 

how they make nerves.132 

cells in the gray substance 
of the brain.132 


all living things built by 

cells.132, 136 

operation of cells in the egg 

during incubation.133 

Cellular tissue, structure of. ... 38 

Cementum.181 

Cerebellum, functions of..332 

Change, constant in the system. 121 
Chemical laws controlled by 

vital.383 

Chest, framework of. 88 

compression of.95, 394 

Chin, possessed only by man.. 30 

Choroid coat of the eye.295 

Chyle. 58 

Chyme. 51 

Ciliary processes.292 

Circulation, its apparatus. 64 

double. 73 

affected by emotions of the 

mind.239 

hygiene of.395 

Climate, influence of in causing 

the varieties of the race.. .371 

Cochlea.281 

Coffee, influence of on health. .408 
Cold, depressing influence of. .398 

sometimes a stimulant.400 

Cold-blooded animals.106 

Collar bone.88, 190 

Concert of action in formative 

and other vessels.... 110-116 
Conscience, not possessed by 

animals.27, 360 

Consciousness, its evidence 

against materialism.344 

Consonants, incorrectness of 

the common definition... .264 
nasal reverberation 4he pecu¬ 
liarity of some of them.. .262- 

Convolutions of the brain.145 

Convulsions.165 

Coracoid process.190 

I Coronary arteries.80 

Corrugator supercilii. .. .228 

Cranium, bones of.175 

Creator, belief in and knowl¬ 
edge of result of the power 

of abstract reasoning.360 

I Cricoid Cartilage.249 

; Crystalline lens.295 






































































INDEX. 


449 


Cuticle.119 

made up of cells.130 

Daisy. 18 

Deaf and Dumb.223 

why they are dumb.267 

teaching them to talk.268 

Death.387 

Deformity, how produced.402 

Deglutition. 47 

Dentals..261 

Dentine.181 

Diaphragm. 89 

Digastric muscle.206 

Digestion. 42 

hygiene of..53, 391 

Disease, summary of its causes. 409 

prevention of.410 

Distinct vision, point of.312 

Dog, his muscles of expression.237 

sagacity of.358 

Dome, principles of seen in the 

cranium.177 

Domestication, influence of. .. .371 

Drowning explained. 97 

explanation of .some cases of 
restoration.109 

Ear, its shape.275 

its bones.276 

its winding passages.277 

Egg, section of.134 

how cells develop the bird... 135 

Electricity not nerve force.160 

Elementary substances in ani¬ 
mals and vegetables. 20 

Elbow joint.194 

Emphasis some of the princi¬ 
ples of.269 

Enamel, structure of.131, 182 

Epiglottis.48, 216, 256 

Erect posture of man.30 

Ethiopian variety of the race ; 
evidence of its existence 

in early ages.374 

Excretion, by what organs per¬ 
formed.118 

Exercise, influence of on diges¬ 
tion . 54 

on the circulation.395 

on the development of the 
body.396 


on the heat of the body.398 

Experience, no transmission of 

it in animals as in man... .362 
Expiration, mode of perform¬ 
ing. . 90 

Expression, nerve of in the 

face paralyzed.157 

Expression effected by muscles.222 
its principal muscles in man.224 

in animals.236 

Eye, optical instrument.287 

nerves of.158 

muscles of.208 

in itself inexpressive.226 

its parts.290-292 

how it accommodates itself 
to objects at different dis¬ 
tances.298 

its defences.315 

Eye-brow, its agency in expres¬ 
sion.225, 228 

Face, muscles of..202, 228 

its capabilities in expression.239 

training of its muscles. 240 

state of its muscles after 

death.242 

Facial angle.336 

Far-sightedness.299 

Fat, uses of..40 

Fear, action of muscles of face 

in.235 

Fibrillae muscular.130, 196 

Fingers, arrangement of ten¬ 
dons in.215 

Fishes, respiration of. 98 

spinal column in.189 

Food, quantity needed.391 

regularity in taking.393 

Foot, bones of.195 

Fordyce, his experiments on 

heat.107 

Formation and repair, by what 

done.109 


Formative vessels, selecting 

power of.110 

their concert of action illus¬ 
trated in various ways. 110-116 

are really cells.123 

Frog, changes from the tadpole 

state.112 

2 * 








































































450 


INDEX. 


cells seen in the circulation 

in web of the foot... 124 

Frontal sinus.179 

different sizes of.335 

Functions, distinctions be¬ 
tween nutritive and animal. 36 

Ganglions.149 

Gastric juice.'.. 50 

Gills, truly lungs.98 

Gizzard, in birds. 62 

Grace, in the action of the 

muscles.242, 366 

Gradations, doctrine of.. 32 

Grasshopper, respiration in.... 99 
Gray substance of brain... 132, 147 
amount of compared with 

the white substance.333 

dependence of mind on.334 

Gymnastics.404 

Hand, really possessed only by 

man. 29 

variety of its motions.218 

Harvey, discoverer of the cir¬ 
culation. 72 

Head, bones of.175 

Hearing, apparatus of.274 

nerves of.282 

organ of in fishes.284 

in birds. .285 

Heart, a forcing and suction 

pump. 65 

its action illustrated.69 

double. 73 

valves in. 74 

its auricles and ventricles . .74-79 

front view of. 80 

map of. 81 

situation of. 82 

sounds of. 83 

its sac. 84 

its number of beats.85 

insensibility of to touch.156 

Heat of the body, how main¬ 
tained.104, 397 

where made.105 

sources of the fuel for it.105 

on what its amount depends. 106 

effect of exercise on it.106 

degrees of heat in the air 
which the body will bear.. 107 


its uniformity in man... 107, 398 

Herbivorous animals.43, 60 

Hibernation.108 

Hoarseness, cause of.256 

Honeycomb, the perfection of 

it as a structure.351 

Human race, varieties of.367 

Humerus.190 

Hunger, cause of and seat.... 54 

Hydra.23, 26 

cells in.125 

Hygiene, how its principles are 

learned.390 

Hyoid bone.183, 248 

Tlium.175 

Images on retina, inverted... .293 
why the mind sees them erect.299 
rapidity of their succession. .314 

minuteness of..312 

Immortality of man. 28 

known only from Revelation. 345 
Insanity, result of disease in 

the organization..320 

some of its causes noticed. ..407 
influence of sleeplessness in 

producing it.406 

Inspiration, mode of performing. 90 
Instinct, more mysterious than 

reason.348 

uniformity of its action.349 

its perfection.351 

exhibited in communities of 

animals.352 

blindness of it.354-356 

Involuntary muscles.162 

not trained like \oluntary. . . .326 

Iris.294 

Iron, in the blood.20 

carried in cells.127 

Jaw, lower.181 

its digastric muscle.207 

Joints, lining of.195 

Knowledge, communicated only 
by muscles.222 

Labials.261 

Lacteals. 58 

Language, result of the power 
of abstract reasoning.360 








































































INDEX. 


451 


Larynx.248-252 

Laughter, by what muscles 

done.224 

Leaves, discharge oxygen and 

absorb carbonic acid gas. .104 
Lever, the three kinds of exem¬ 
plified in the muscles.198 

Ligaments, of the hand.193 

of the wrist and ankle.206 

vocal. . .250 

Life, its origin and processes.. .381 

its nature unknown.382 

differs from other forces.382 

controls chemical forces.383 

sometimes dormant.384 

its connection with the soul.385 

Light, refraction of.. 287-289 

Lips, their agency in speech.. .261 
Lime, in animals and vegeta¬ 
bles . 20 

Lobworm, respiration of.. 98 

Locomotion, distinguishing ani¬ 
mals from plants.21 

Lungs, structure of.86 

Lymphatic absorbents.59 

what they absorb.117 

Man, distinctions between him 

and animals. .27-31, 347, 365 

their definiteness.337 

Mastication. 43 

Materialism, tendency to in 
some physiologists, and 

why....339 

Meals, intervals between.393 

Mechanical disadvantage under 

which muscles act.203 

Mesentery, plan of. 57 

Metacarpus.192 

Metatarsus.194 

Mind, dependence of on the 

brain.319 

rapidity of its communica¬ 
tion with all parts of the 

body.^321 

training of in the use of the* 

senses and muscles.322 

its supposed indestructibility .339 
sources of evidence as to the 
nature of its union with 
the body.339-347 


I intimacy of its union with 

the body.338 

influence of mind on diges¬ 
tion.393 

Miracle, supposition of in caus¬ 
ing the varieties of the 

race.377 

Monboddo's notion.347 

Motion, spontaneous.22, 142 

automatic. 24 

involuntary.162 

Mouth, agency of in expression.224 

Mucous membranes.40 

Muscles.38 

their structure.130 

mode of action.196 

of arm.199 

of face and neck.202 

of the eye.208 

of larynx.251 

various shapes of.210 

combined motions of 210,216,220 

variety of size of.214 

constant change in action of. 217 
all knowledge communica¬ 
ted by muscles.222 

skill in their use.324 

their associated action.327 

Muscular sense.220, 308 

Nails, made by cells.131 

Nasal sounds.262 

National differences.369 

Nature, its inner beauty great¬ 
er than its outer.137 

Near sightedness.299 

Nerves made from cells.131 

terminations of..150 

healing of.152 

different sets of for different 

purposes.153 

for different sensations.154 

for different motions.156 

nerves of the eye.158 

of the ear.281 

Nervous system, distinguishing 

animals from vegetables.. 23 


Nerve-force, not identical with 

electricity.ICO 

Nitrogen, how far peculiar to 

animals. .. 27 









































































452 


INDEX. 


Nictitating membrane. 

Nose, bones of.. 

nerves of. 

Note, variations of, how pro¬ 
duced in wind instruments.246 

in reed.247 

in the vocal instrument.257 

Oesophagus described.49 

Objects, how they are pictured 

on the retina.292 

how the eye is adjusted to 
their different distances.. .298 
how we estimate their motion.313 

Optic nerves, crossing of.305 

Organ, flute stop of.245 

Organic life, distinguished from 

animal life.24, 139 

Organized and unorganized 

substances. 13 

difference between in per¬ 
manency. .. 15 

in regularity. 17 

in size. 19 

in structure. 20 

organized built by cells.136 

Ostrich, respiratory apparatus of. 100 

Oval form of head.... 373 

Oxygen, absorbed by the lungs. 101 
exhaled by plants.104 

Pacinian corpuscles.151 

Pain, a warning of danger... .154 
expression of the counten¬ 


ance in.225 


Papillae of the skin.. 

.120, 150 

Patella.. 

.183, 194 

action of the muscles on... .205 

Pelvis. 


Perspiration, influence of in 

enabling the body to 

bear 

very hot air. 

.108, 398 

Petrous (rock-like) bone.. 

. 180, 275 

Pharynx. 

.47 

Phrenology. 

.334 

Plants, distinctions between 

them and animals... 

. 21 

Pleura . 

.88 

Plexuses of nerves. 

.149 

Prognathous type of head 

.373 

Pulse, cause of. 

.. .. 65 

Pylorus. 

.51 


. Quickness of action the chief 
object in most muscles. 200 

Radius.192 

Rage, action of muscles of 

face in.234 

Reaction against cold, how pro¬ 
duced.400 

Reason, not confined to man.. .348 
of a lower order in animals. .362 
Reasoning abstract, peculiar to 

man.. .27, 359 

source of language.........360 

of a belief in a creator.360 

of knowledge of right and 

wrong.360 

Reed instruments.247 

Reflex action explained.162 

Respiration, its apparatus. 86 

mechanism of. 88 

hygiene of. 394 

Respiratory apparatus of fishes. 98 

of insects. 99 

of birds.iu 0 

Retina, structure of.296 

images formed on.292 

Revelation, its evidence against 

materialism. 345 

testimony of in regard to 
unity of origin of the race. 378 
Reverie, involuntary action of 

muscles in.167, 327 

Ribs, arrangement of.. 88 

movement of in respiration.. 92 

Ringentes (muscles).237 

Robinet, his doctrines.31 

Sacrum.. 

Salivary glands. 45 

Scapula. 190 

Scintillantes (muscles).237 

Secretions, formed from the 

blood. 116 

by cells.129 

Sebaceous glands. 120 

Seeing, a process that is learn¬ 
ed. 305 

Semicircular canals.278, 282 

Sensation, distinguishes ani 

mals from plants. 22 


317 ' Pyramidal type of head.373 

180 
154 







































































/ 

INDEX. 

463 

a compound act. 

141 

Sutures of the skull.. 


what is necessary to it. 

142 

Sweat glands... 


special and common. 

Sensibility, various in different 

154 

Sympathetic system of nerves. 

.169 

parts.. 

,155 

Talking, how learned.. 

..265 

Serous membranes. 

41 

Tarsus.. 


Silex in plants., 

. 20 

Tailor-bird’s nest. 


Silkworm, its Changes illus¬ 


Tea, influence of on health... 

.408 

trating concert of action 


Tear apparatus. 


in the formative vessels... 

.113 

Teeth, different kinds. 

. 43 


Skeleton, description of.173 

Skin, structure and functions of. 119 

hygiene of.397 

great sensibility of.155 

Somnambulism.330 

Song, how it differs from speech.268 

why more difficult.270 

Soul, its connection with the 

vital force.385 

Sound, how produced and trans¬ 
mitted.272 

difference in transmission 
through solids, liquids and 

gases.273 

Sound musical, how it differs 

from noise.271 

how its not#is varied in wind 

instruments.246 

how in reed.247 

how in the vocal instrument.253 
Speech, instruments for imita¬ 
ting it.264 

Species, how it differs from 

variety.371 

Spinal column... 88 , 173, 183-187 

of birds.188 

of fishes and reptiles.189 

deformity of, how caused... .403 

Spinal cord or marrow.153 

its functions.164, 167 

Squinting..209, 301 

Stammering..*.267 

Stereoscope. .302 

Stomach, used in two senses... 15 
distinguishing animals from 

plants. 21 

its three coats.41 

its muscular coat.51 

difference of this organ in 

different animals.60 

Stigmata. 99 

Superbus muscle.230 


structure of..131, 181 

nerves in.151 

why second set needed.182 

Tendons.38, 197 

Temporal bone.177 

Thaumalrope.315 

Thigh bone.194 

Thirst, cailse of and seat.55 

Thoracic duct. 59 

Throat disease.259 

Thyroid cartilage.248 

Tobacco, its influence on health.408 
Toggle-joint, exemplified in the 

joints of the body.217 

Tongue, its variety of molion ..210 

its agency in speech.260 

Training of the muscles and 

the senses.325 

Tubuli of the nerves.147, 152 


Ulna 


.192 


Valves of the heart.74, 78 

of the aorta. 77 

of the veins.67 

Vanishing movement in the 

voice.269 

Veins, structure and situation 

of..65 

why the blood accumulates 

in them at death. 71 

what they absorb.118 

Ventilation, effects of, defective. 103 

Ventriloquism.271 

Vertebrae described.184 

Violin, imitation of the voice 

with.257 

Vision, apparatus of.287 

why commonly single.300 

sometimes double.301 

vision mostly a mental pro¬ 
cess .309-311 










































































454 


INDEX. 


how the figure, size and dis¬ 
tances of objects are 

known.305-308 

mistakes in, how rectified.. .308 

Visual angle.305 

Vitreous table of the bones of 

the skull.... .17G 

Vocal ligaments.250 

Vocal muscles, education of.. .258 

trained by the ear.258, 266 

Voice, chief means of com¬ 
municating knowledge... .222 
its apparatus a musical in¬ 
strument .243 

articulation of.259 

Waste of the system, by what 

organs thrown off... .118, 397 


influence of its retention... .397 

Wasp’s nest.352 

Water-scorpion, respiration of. 99 
Weeping, action of the mus¬ 
cles in.225 

Whale, arrangement for catch¬ 
ing its food. 45 

its reservoirs for containing 

arterial blood. 97 

Whispering, how done.263 

White substance of the brain.. 147 

office of.334 

Wind instruments.245 

Zoological provinces.370 

Agassiz’s analogy in this re¬ 
spect fails in regard to 
man.375 
















































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